Andreas Schiller, Sandra Jenatsch, Balthasar Blülle, Miguel Angel Torre Cachafeiro, Firouzeh Ebadi, Nasim Kabir, Mostafa Othman, Christian Michael Wolff, Aïcha Hessler-Wyser, Christophe Ballif, Wolfgang Tress, and Beat Ruhstaller

The Journal of Physical Chemistry Letters, 15, 11252−11258.

DOI: 10.1021/acs.jpclett.4c02403

This research paper investigates the impact of illumination on ion conductivity in perovskite solar cells (PSCs), highlighting the complex interplay between ionic and electronic charge transport. Using drift-diffusion simulations to reproduce experimental impedance spectroscopy results, the authors discovered that the increase in capacitance observed at low frequencies under illumination is mainly caused by changes in electronic currents that emerge naturally as a consequence of the mixed electronic-ionic conduction in the perovskite. The simulations show how the changes in the alternating electronic currents occur due to the screening of the alternating electric field by oscillating ions within the active layer of the PSCs. 

A key contribution of this study is the introduction of a novel characterization technique to detect the presence of photo-enhanced ion conductivity. This technique is based on analyzing the frequency shift of the capacitance onset at different illumination intensities. The researchers extracted the frequency at which the capacitance reaches a specific value between the plateaus at lower and higher frequencies. By plotting the difference in the extracted frequency at various illumination intensities compared to in the dark, they observed distinct qualitative differences in the frequency shift patterns, depending on the presence of a photoconductive effect on the ions. 

The findings revealed that if there is no photoconductive effect, the derivative of the frequency shift decreases at lower illumination intensities. In contrast, in simulations mimicking a photoconductive effect, the derivatives increase with decreasing illumination intensity. To capture these distinct patterns, the technique requires a series of capacitance measurements over several orders of magnitude in illumination intensity. The illumination intensity range should be carefully chosen to observe both the constant derivative decrease and the change in the derivative at lower intensities. 

The researchers successfully applied this method to four different PSCs with varying active materials, confirming the presence of photo-enhanced ion conductivity in all the devices. This novel technique offers a simple and effective way to detect photo-enhanced ion conductivity in PSCs. It utilizes impedance measurements on fully integrated devices, making it practical for real-world applications. By contributing to a better understanding of the complex interplay between ionic and electronic charge transport, this technique can ultimately lead to improved device performance and stability. 

Fluxim's Setfos simulation software and Paios measurement platform were crucial to this research. Setfos enabled the creation of a drift-diffusion model of a PSC, simulating the behavior of the active layer—treated as a mixed electronic-ionic conductor—under different illumination conditions. This simulation was instrumental in understanding the influence of ionic charge carriers on capacitance and conductance. Paios, equipped with its calibrated white LED light source, was used to perform Electrochemical Impedance Spectroscopy (EIS) measurements on the PSCs to detect photoconductive effects on the ions. 

These findings emphasize the need for further research to develop a complete understanding of the phenomenon, as the interaction between ionic and electronic charge transport plays a significant role in the performance and stability of PSCs.

Aeberhard, U., Natsch, N., Schneider, A., Zeder, S.J., Carrillo-Nuñez, H., Blülle, B. and Ruhstaller, B. (2024),

Sol. RRL 2400492.

https://doi.org/10.1002/solr.202400492

This research paper examines reverse-bias breakdown in all-perovskite tandem solar cells, particularly under partial shading conditions, and highlights how nonuniform active area quality, such as variations in mobile ion concentration, can impact their performance. The study uses a multi-scale simulation approach to demonstrate that an increase in mobile ion density significantly reduces the breakdown voltage and can lead to localized current hot spots in large-area modules. The authors suggest that these hot spots, caused by fluctuating mobile ion concentration, are potential degradation centers in the solar cells. They also suggest further investigation into factors like unintentional doping and additional breakdown mechanisms to better understand and improve the performance of these solar cells.

How SETFOS Was Used to Study Reverse-Bias Breakdown

The authors of the research paper use the device simulation tool SETFOS to perform cell-level simulations on all-perovskite tandem solar cells. Here's a breakdown of its role:

Drift-diffusion Simulation: SETFOS is used to simulate the behavior of charge carriers within the solar cell under a large reverse-bias voltage. This helps researchers visualize the band profile, or the energy levels of electrons within the device's various layers.

Mobile Ion Consideration: The simulations in SETFOS incorporate the effects of mobile ions within the perovskite layer, a crucial aspect that influences the breakdown voltage.

Coupling with Quantum Transport Simulation: The data from SETFOS, including the band profile and quasi-Fermi levels, are then used as input for a separate quantum transport simulation tool, PVnegf. This allows for a microscopic examination of the tunneling breakdown current.

Iterative Analysis: The tunnel generation rates, calculated in PVnegf, are fed back into SETFOS. This iterative process, with information exchanged between SETFOS and PVnegf, continues until the tunneling current converges, providing an accurate representation of the breakdown phenomenon.

Generating JV Curves: Through this coupled simulation approach, SETFOS ultimately helps generate current density-voltage (JV) curves for the all-perovskite tandem solar cell, even under reverse-bias conditions. These JV curves are essential for understanding how the device performs near its breakdown voltage.

In summary, SETFOS acts as the foundation for the cell-level simulations, providing crucial data about charge transport and mobile ion behavior, which is then combined with quantum transport calculations to comprehensively study reverse-bias breakdown in all-perovskite tandem solar cells.

Using Laoss to Simulate Large-Area Solar Module Behavior

Simon J. Zeder, Balthasar Blülle, Beat Ruhstaller, and Urs Aeberhard,  Opt. Express 32, 34154-34171 (2024)

https://doi.org/10.1364/OE.522953

This paper presents a multiscale optical model developed to accurately quantify photon recycling (PR) and luminescent coupling (LC) in optoelectronic devices such as solar cells and LEDs. Photon recycling, the process of photon emission, re-absorption, and re-emission, can significantly enhance device efficiency, particularly in materials like GaAs, metal halide perovskites and even crystalline silicon. To accurately account for re-absorption effects, the model treats light absorption and emission equally, considering the full spectrum of internal modes within the device. This approach stands out from conventional methods, which focus solely on exterior-coupled modes.

The framework integrates two key propagation models: 

Coherent Wave-Optical Model: Applied to thin-film layers where light interference effects are significant, avoiding unphysical divergencies for emitters embedded in absorbing media and ensuring consistency with detailed balance principles. 

Incoherent Ray-Optical Model: Used for optically thick layers where coherence is lost, treating phase relations as irrelevant. 

The model also accounts for light scattering at textured surfaces, essential for devices like perovskite –silicon tandem solar cells. By merging these approaches, the paper provides a robust framework for computing local emission, re-absorption, and energy flux rates in devices with complex structures. Importantly, this allows for a detailed understanding of the impact of photon recycling on device performance, including enhanced external quantum efficiency (EQE) in LEDs and increased open-circuit voltages in solar cells. 

The model is validated through comparisons with analytical solutions, showing excellent agreement, and applied to a textured perovskite solar cell showcasing its capabilities. This validation confirms that the model can reliably be applied to real-world devices, offering a powerful tool for optimizing the performance of next-generation optoelectronic systems. 

Key Takeaways: 

∙ Comprehensive multiscale approach merging coherent and incoherent light models. 

∙ Applicability to complex textured devices like perovskite solar cells and LEDs. 

∙ Quantification of local re-absorption and energy flux rates. 

∙ Validation through comparison with analytical solutions. 

Othman, M., Jeangros, Q., Jacobs, D. A., Futscher, M. H., Zeiske, S., Armin, A., Jaffrès, A., Kuba, A. G., Chernyshov, D., Jenatsch, S., Züfle, S., Ruhstaller, B., Tabean, S., Wirtz, T., Eswara, S., Zhao, J., Savenije, T. J., Ballif, C., Wolff, C. M., & Hessler-Wyser, A. (2024). Energy & Environmental Science. The Royal Society of Chemistry.

DOI: https://doi.org/10.1039/D4EE00901K

This study investigates the effects of cationic alloying in cesium-formamidinium perovskite films on optoelectronic properties and solar cell performance. It finds that precise Cs+ tuning minimizes structural faults and enhances photoconductivity, with encapsulated devices maintaining 85% of initial efficiency after 1400 hours under continuous illumination, providing insights into defect tolerance and stability mechanisms in perovskite materials.

Fluxim's Research Tools

In the study, Fluxim's Paios system was used for conductivity measurements, and Litos for accelerated aging tests under thermal and photonic stress, evaluating the stability of perovskite solar cells.

Almora, O., López-Varo, P., Escalante, R., Mohanraj, J., Marsal, L. F., Olthof, S., & Anta, J. A. (2024). arXiv:2402.00439 [physics.app-ph]

https://doi.org/10.48550/arXiv.2402.00439

The paper analyzes degradation in perovskite solar cells using impedance spectroscopy, focusing on NiOx passivation. It identifies how interface treatments influence device performance, with some treatments stabilizing and others inducing degradation. Simulation tools model transport properties to understand these effects.

How Setfos Was Used

Fluxim's Setfos simulation software was employed to model the transport properties and electrical responses of passivated-NiOx perovskite solar cells. This facilitated the understanding of how modifications at the hole transport layer-perovskite interface, due to various passivation methods, impact the cells' performance and operational stability.

Thiesbrummel, J., Shah, S., Gutierrez-Partida, E. et al.

Nat Energy (2024).

https://doi.org/10.1038/s41560-024-01487-w

The study reveals that the dominant factor in the degradation of perovskite solar cells (PSCs) under operational conditions is mobile ion-induced internal field screening, significantly reducing efficiency mainly due to current density reduction, without major bulk or interface quality degradation.

How Setfos was used

Setfos was used to simulate the impact of increasing mobile ion density on PSC performance, demonstrating that higher ion density leads to enhanced internal field screening, reducing charge extraction efficiency and contributing significantly to early degradation losses in PSCs.

Valastro, S., Calogero, G., Smecca, E., Bongiorno, C., Arena, V., Mannino, G., Deretzis, I., Fisicaro, G., La Magna, A. and Alberti, A. (2024), Sol. RRL 2300944.

https://doi.org/10.1002/solr.202300944

The research demonstrates printable carbon-based perovskite solar cells infiltrated with CsPbI3:EuCl3 outperform AVA-MAPbI3 cells, showcasing reduced hysteresis, stable efficiency under continuous light, and notable durability with multiple reusability cycles. Achieving a peak power conversion efficiency of 16.72%, the CsPbI3:EuCl3 variant emerges as a promising candidate for sustainable and efficient photovoltaic technologies, with implications for enhancing the environmental sustainability of solar energy generation​

How Setfos was used

Setfos tool was utilized for 1D transient-mode electro-optical simulations of the fabricated mesoporous carbon perovskite solar cells (mC-PSCs), incorporating both anion and cation migration within the active regions. This involved simulating the charge generation profile using the transfer-matrix method, calibrated with wavelength-dependent complex refractive indices of all layers, and coupling it with a drift-diffusion charge transport solver to account for charge trapping, recombination, and ion migration. The simulations aimed to replicate the measured J–V curves' main features, with layer-specific electrical parameters calibrated based on reasonable initial values from literature.

S. Ravishankar, L. Kruppa, S. Jenatsch, G. Yan and Y. Wang, Energy Environ. Sci., 2024,

DOI: 10.1039/D3EE02013D.

The paper discusses a novel method for analyzing solar cell operation, focusing on perovskite solar cells (PSCs). It addresses a gap in understanding the equivalence of time-domain and frequency-domain data in solar cell analysis. The study introduces a new approach to extract a previously inaccessible time constant from frequency domain data, which correlates with charge extraction speed in transient measurements. This method is validated through simulations and experimental data, offering a more comprehensive understanding of charge carrier dynamics in solar cells, particularly regarding charge collection efficiency.

How Setfos was used

SETFOS was utilized in the paper for conducting drift-diffusion simulations. These simulations were part of the study's methodology to characterize perovskite solar cells (PSCs) using various techniques, including transient photovoltage (TPV), transient photocurrent (TPC), intensity-modulated photovoltage spectroscopy (IMVS), intensity-modulated photocurrent spectroscopy (IMPS), and impedance spectroscopy (IS)​

S. Alam, H. Aldosari, C. E. Petoukhoff, T. Váry, W. Althobaiti, M. Alqurashi, H. Tang, J. I. Khan, V. Nádaždy, P. Müller-Buschbaum, G. C. Welch, F. Laquai

Adv. Funct. Mater. 2023, 2308076. https://doi.org/10.1002/adfm.202308076

This paper investigates the impact of thermal annealing on PM6:Y6-based organic solar cells, focusing on performance degradation due to structural and morphological changes at elevated temperatures. It finds that VOC and FF significantly decrease with annealing above 140°C due to altered charge transport and extraction.

How Setfos was used

Using SETFOS software, the study simulates device performance, correlating optical-electrical properties with device parameters to understand the degradation mechanisms and guide future improvements.

How Paios was used

Paios was used to measure transient photocurrent, photo-voltage, and charge extraction properties, providing insights into charge generation, recombination, and extraction mechanisms, helping to understand the performance drop at elevated annealing temperatures.

Bandgap Tunable Perovskite for Si-Based Triple Junction Tandem Solar Cell: Numerical Analysis-Aided Experimental Investigation

Jia-Ci Jhou, Ashish Gaurav, Hsin-Ting Lin, and Ching-Fuh Lin

ACS Applied Energy Materials 2023 6 (18), 9434-9445

DOI: 10.1021/acsaem.3c01344

Researchers developed a new technique to fabricate perovskite absorbing layers for multijunction solar cells, achieving a record power conversion efficiency of 26.4%. This technique involves a double-sided sandwich evaporation process that allows for precise control over the halide ratio and B-site doping of the perovskite absorber layers. The resulting triple-junction tandem solar cell exhibits significantly higher efficiency than previous designs.

How Setfos was used.

theoretical insight for the optimal perovskite thickness was gained using Setfos by taking into account the reflection of the bottom cell, so the thickness of the top layers could be reduced.

Warby, J., Shah, S., Thiesbrummel, J., Gutierrez-Partida, E., Lai, H., Alebachew, B., Grischek, M., Yang, F., Lang, F., Albrecht, S., Fu, F., Neher, D., Stolterfoht, M.,

Adv. Energy Mater. 2023, 2303135.

https://doi.org/10.1002/aenm.202303135

This research addresses the discrepancy between open-circuit voltages (VOC) and internal voltages in perovskite solar cells, often attributed to non-radiative recombination losses. The study extends classical theories from silicon solar cells to explain the mismatch through partial resistances/conductivities of carrier types. It also reveals how mobile ions in perovskite cells contribute to this mismatch, explaining phenomena like light soaking and aging-induced VOC losses. These insights offer new perspectives on degradation issues and guide principles for optimizing VOC to enhance perovskite solar cell performance.

How Setfos was used

Band diagram simulation of perovskite cells with ions

Moritz C. Schmidt, Emilio Gutierrez-Partida, Martin Stolterfoht, and Bruno Ehrler

PRX Energy 2, 043011 – Published 13 November 2023

https://doi.org/10.1103/PRXEnergy.2.043011

This study reveals that analyzing capacitance transients in perovskite solar cells is more complex than previously thought. It demonstrates that the direction of these transients is influenced by the cell's layer dominating capacitance modulation, not by the polarity of migrating species. This highlights the significant role of transport layers in characterizing mobile ions in perovskites.

Setfos was used

To investigate the role of the polarity of mobile ions in capacitance measurements the researchers simulated the behavior of the capacitance as a function of time after a voltage pulse. The Drift-Diffusion module in Setfos was used to simulate the capacitance transients.

Juhui Oh, Ju-Hyeon Kim, Yong Ryun Kim, Ardalan Armin, Sanseong Lee, Kiyoung Park, Hongkyu Kang, and Kwanghee Lee

ACS Applied Materials & Interfaces 2023 15 (36), 42802-42810

https://doi.org/10.1021/acsami.3c08028

This research discusses the challenge of balancing transparency and efficiency in transparent organic solar cells (T-OSCs) for smart solar windows. A new tungsten oxide (WO3)-based multilayer top electrode is presented that achieves both high photopic transmittance (46.7%) and power conversion efficiency (7.0%), with superior light utilization and thermal stability. This development offers new directions for creating efficient, transparent solar cells for energy-harvesting windows.

How Setfos was usedSetfos

To predict the transparent OSC performance, optical simulation was conducted with the commercial software Setfos using n and k values obtained from ellipsometry.

Sarmad Feroze, Andreas Distler, Karen Forberich, Iftikhar Ahmed Channa, Bernd Doll, Christoph J. Brabec, Hans-Joachim Egelhaaf,

Solar Energy, Volume 263, 2023, 111894, ISSN 0038-092X,

https://doi.org/10.1016/j.solener.2023.111894

The 2022 global PV installations accounted for 5% of electricity consumption. To reach 2 TWP annually by 2030, leveraging existing urban surfaces is vital. BAPV/BIPV transform buildings into energy producers. Currently dominated by silicon PV modules, the market has underutilized Organic Photovoltaics (OPV), a cost-effective, customizable, and flexible alternative for BIPV applications. This study analyzes OPV's outdoor performance compared to monocrystalline silicon modules, aiming to provide insights for forecasting the annual energy yield of building-integrated OPV modules, advancing OPV technology for BIPV applications.

How Setfos was used

Setfos software by Fluxim AG was used for optical simulations to evaluate absorption in the active layer of the OPV device.

Sandheep Ravishankar, Zhifa Liu, Yueming Wang, Thomas Kirchartz, and Uwe Rau

PRX Energy 2, 033006 – Published 2 August 2023

https://doi.org/10.1103/PRXEnergy.2.033006

Researchers present a model for the frequency and time domain optoelectronic response of perovskite solar cells (PSCs). The model emphasizes the role of charge carrier exchange between the perovskite and the transport layer. The study identifies that the time constants measured in the frequency domain spectra of PSCs are mainly influenced by the charge carrier extraction velocity at the perovskite/transport layer interfaces, rather than recombination. This understanding is crucial for quantifying recombination and resistive losses that impact the performance of the solar cell.

Drift-diffusion simulations are performed using SETFOS developed by Fluxim AG

Jonas Diekmann, Francisco Peña-Camargo, Nurlan Tokmoldin, Jarla Thiesbrummel, Jonathan Warby, Emilio Gutierrez-Partida, Sahil Shah, Dieter Neher, and Martin Stolterfoht

The Journal of Physical Chemistry Letters 2023 14 (18), 4200-4210

DOI: 10.1021/acs.jpclett.3c00530

This scientific article discusses the impact of mobile ions on perovskite photovoltaic devices and the challenges in accurately quantifying mobile ion densities. The study evaluates several experimental methodologies, including charge extraction by linearly increasing voltage (CELIV) and bias-assisted charge extraction (BACE), as well as frequency-dependent capacitance measurements.

The findings show that CELIV underestimates ion density and is not suitable for accurate quantification. BACE, on the other hand, can accurately reproduce ion density as long as it is lower than the electrode charge. The study also demonstrates that low-frequency Mott-Schottky analysis can provide accurate ion density values for high excess ionic densities typical of perovskites. Overall, the methods presented in this study enable accurate tracking of ionic densities in perovskite devices and a deeper understanding of ionic losses and device aging.

How was Setfos Used?

SETFOS was used in this work to simulate the impact of mobile ions on the performance of perovskite solar cells. The parameters related to mobile ions were implemented in the drift-diffusion module of Setfos. This allowed the researchers to include mobile ions in their simulations and recreate the observed JV-hysteresis in the cells over a wide range of scan speeds. The simulations also verified that losses in the performance characteristics of JSC, VOC, and FF could be recreated

Huo, M.; Hu, Y.; Xue, Q.; Huang, J.; Xie, G.

Molecules 2023, 28, 2145.

https://doi.org/10.3390/molecules28052145

Organic/inorganic hybrid materials, like PVA and TTIP, show excellent optical properties for multilayer antireflection films. With a tunable refractive index & low haze, they achieve high transmittances up to 99.3%. Applied to perovskite solar cells, they boost efficiency from 16.57% to 17.25%.

The hybrid material/CA stack and the hybrid material/PMMA stack were simulated by Setfos.

Salem, M.S.; Shaker, A.; Abouelatta, M.; Saeed, A.

Polymers 2023, 15, 784.

https://doi.org/10.3390/polym15030784

Researchers have designed and analyzed perovskite/organic tandem solar cells (TSCs) using a full optoelectronic simulator (SETFOS).

A lead-free ASnI2Br perovskite top subcell is paired with a DPPEZnP-TBO:PC61BM heterojunction organic bottom subcell, based on previous experimental work. Calibration shows strong agreement between simulation and experimental data.

The optimized tandem cell achieves 14% efficiency with further improvements possible through concurrent optimization and defect reduction. This study provides valuable insights and directions for enhancing lead-free perovskite/organic TSC efficiency.

Pietro Caprioglio, Joel A. Smith, Robert D. J. Oliver, Akash Dasgupta, Saqlain Choudhary, Michael D. Farrar, Alexandra J. Ramadan, Yen-Hung Lin, M. Greyson Christoforo, James M. Ball, Jonas Diekmann, Jarla Thiesbrummel, Karl-Augustin Zaininger, Xinyi Shen, Michael B. Johnston, Dieter Neher, Martin Stolterfoht & Henry J. Snaith

Nat Commun 14, 932 (2023).

https://doi.org/10.1038/s41467-023-36141-8

Wide-gap perovskites suffers from Voc- and Jsc-deficit, but what's the reason and how to solve it?

Researchers from the groups of professors Henry J. Snaith and Martin Stolterfoht recently demonstrated starting from drift-diffusion simulation studies that a poor band-alignment with the electron transporting layer causes the Voc-deficit, while mobile ions obstacle the charge extraction causing Jsc losses. The voltage losses were solved by inducing the growth of a low-dimensional perovskite with a surface treatment based on guanidinium bromide (GuaBr) or imidazolium bromide (ImBr). To improve the charge extraction, they modified the hole-transporting layer applying an ionic interlayer (TEA-TFSI) or replaced it with self-assembled monolayer (SAM).

They used the simulation software Setfos from Fluxim AG to reveal that the hole-transporting layers enhance the charge extraction by inducing a stronger electric field at the interface with the perovskite.

Li, Y., Wu, X., Zuo, G., Wang, Y., Liu, X., Ma, Y., Li, B., Zhu, X.-H., Wu, H., Qing, J., Hou, L., Cai, W.,

Adv. Funct. Mater. 2022, 2209728.

https://doi.org/10.1002/adfm.202209728

Efficient electron transport layer (ETL) based on a novel n-n heterojunction arrangement for organic photovoltaics (OPV).

The group of Whanzu Cai at the Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials stacked an n-type conjugated film (PNDIT-F3N) with an n-type small molecule film (Phen-NaDPO) achieving a water-fall like alignment of electron transport energy levels. Devices with the n-n heterojunction ETL showed performance increase of up to 30% compared to control devices based on the isolated PNDIT-F3N or Phen-NaDPO ETLs.

They used the characterization tool Paios to investigate the charge extraction and recombination lifetimes with transient photocurrent (TPC) and transient photovoltage (TPV) measurements, respectively. Both extraction and recombination lifetimes improved by up to 100% for the devices with the n-n heterojunction compared to Phen-NaDPO alone.

van der Pol, T.P.A., Datta, K., Wienk, M.M. and Janssen,

R.A.J. (2022), Sol. RRL, 6: 2200872.

https://doi.org/10.1002/solr.202200872

A modeling approach is developed to correct outcoupled electroluminescence spectra in thin-film organic and perovskite solar cells. The approach takes into account self-absorption, cavity effects, and nonhomogeneous emission profile to yield intrinsic spectrum. The impact of these effects is studied for various device parameters to uncover trends and provide guidelines for a large set of devices.

Optical Modeling: The simulation procedure used here was based on Dyson et al. where the outcoupled spectrum is calculated using Setfos for a 1 nm emitter layer located in the active layer

Weitz, P., Le Corre, V. M., Du, X., Forberich, K., Deibel, C., Brabec, C. J., Heumüller, T.,

Adv. Energy Mater. 2022, 2202564.

https://doi.org/10.1002/aenm.202202564

A method for organic solar cell (OSC) stability testing is presented that aims to provide more unique insight into the causes of degradation patterns of OSCs. The method involves using monochromatic light at high irradiation doses to accelerate isolated degradation mechanisms while monitoring the device with a series of in-situ steady-state and transient electrical measurements.

The experimental results are accompanied by drift-diffusion simulations to localize degradation pathways. PM6:Y6-based OSCs are tested, which are known to show a rather broad range of lifetimes as a function of device architecture, material batches, or degradation conditions. The experiments reveal a degradation mechanism that causes an increased trap-state density inside the PM6:Y6 layer.

The transient simulations suggest that these states are formed at or around the interface between the PM6:Y6 and the electron transport layer. Furthermore, the surprisingly dominant impact of the illuminating wavelength on the degradation pattern is evidenced.

Lastly, the degradation rate of the devices scales linearly with light intensity, making high intensity and spectrally selective degradation the most promising way to accelerate stability testing for the faster development of stable OSCs.

To localize a mechanism inside the device architecture, the commercial drift-diffusion module of the simulation software Setfos was used.

F. Didier, P. Alastuey, M. Tirado, M. Odorico, X. Deschanels, G. Toquer,

Thin Solid Films, Volume 764, 2023, 139614, ISSN 0040-6090,

doi.org/10.1016/j.tsf.2022.139614.

ABSTRACT

Carbon nanotubes (CNTs), deposited by electrophoretic deposition (EPD), are investigated as selective solar absorbers. First, various kinds of CNTs with different aspect ratios, are dispersed by ultrasound in an aqueous solution of pyrocatechol violet (PV). PV couples to the CNT’s outer walls via π-π stacking interactions and acts as a dispersing agent as well as a charging agent. PV adsorption isotherms on CNT combined with N2 physisorption isotherms are performed to optimize the CNT/PV ratio. In this way, Zeta potentials up to -40 mV are obtained for the dispersed CNTs, which are deposited on platinized silicon wafers by EPD, forming a film. The EPD kinetics are then investigated as a function of the applied electric field (in the 8–20 V cm− 1 range) and are explained through a Sarkar & Nicholson model type. X-ray reflectivity is performed to characterize the density around 1.3 g cm− 3 , and film cohesion is probed by nanoindentation coupled to atomic force microscopy images. The hemispherical reflectance of the samples is measured by spectrophotometers equipped with an integrating sphere, and following from spectra, the absorptance (α) and emittance (ԑ) are calculated. The selectivity of the deposits, based on α and ԑ values, is then discussed as a function of the applied electric field and the coating thickness.

Single-walled CNT deposits, at best, are found to have a solar absorptance of 0.91 and thermal emission of 0.05. Thermal annealing experiments reveal that the coatings could withstand up to 300 ◦C while sustaining selective properties and losing only 21% of the initial yield.

The researchers used Setfos to simulate the absorbed radiation and thermal emission of their films.

Hu, D., Tang, H., Karuthedath, S., Chen, Q., Chen, S., Khan, J. I., Liu, H., Yang, Q., Gorenflot, J., Petoukhoff, C. E., Duan, T., Lu, X., Laquai, F., Lu, S.,

Adv. Funct. Mater. 2022, 2211873.

doi.org/10.1002/adfm.202211873

Abstract

The commercial viability of all-small-molecule (ASM) organic solar cells (OSCs) requires high efficiency, long-term stability, and low-cost production.

However, satisfying all these factors at the same time remains highly challenging. Herein, a volatile solid additive, namely, 1,8-dichloronaphthalene (DCN) is demonstrated to simultaneously enhance the power conversion efficiency (PCE) and the storage, thermal as well as photo stabilities of oligothiophene ASM-OSCs with concise and low-cost syntheses.

The improved PCEs are mainly due to the DCN-induced morphology control with improved exciton dissociation and reduced non-geminate recombination. Notably, the PCE of 16.0% stands as the best value for oligothiophene ASM-OSCs and is among the top values for all types of binary ASM-OSCs. In addition, devices incorporating DCN have shown remarkable long-term stability, retaining over 90% of their initial PCE after dark storage aging of 3000 h and thermal or light stressing of 500 h.

The findings demonstrate that the volatile-solid-additive strategy can be a simple yet effective method of delivering highly efficient and stable oligothiophene ASM-OSCs with excellent commercial viability.

The 1D numerical drift-diffusion module of Setfos was used to simulate the O-ASM-OSCs device J–V characteristics.

Ahmer A.B. Baloch, Omar Albadwawi, Badreyya AlShehhi, Vivian Alberts,

Energy Reports, Volume 8, Supplement 16, 2022,

ISSN 2352-4847,

https://doi.org/10.1016/j.egyr.2022.10.215

What is the worldwide performance of silicon/perovskite solar cells compared to the respective single-junctions?

That is the question that the group of Vivian Alberts from the Research and Development Center of the Dubai Electricity and Water Authority answered by simulating the energy yield and cell temperature depending on the geographical location.

Considering a perovskite solar cell with a bandgap of 1.7eV, tandem cells generate on average 26.7% more energy than silicon solar cells, while dissipating less heat thanks to the higher electrical efficiency. The optimal latitude for tandem performance in the 45◦N to 45◦S range.

With the simulation software Setfos from Fluxim AG they could estimate the theoretical efficiency limit of the tandem device under standard testing conditions (STC) using detailed balance analysis.

Sandheep Ravishankar, Zhifa Liu, Uwe Rau, and Thomas Kirchartz

PRX Energy 1, 013003 – Published 7 April 2022

Capacitance methods, such as capacitance-voltage-frequency measurements, Mott-Schottky analysis, and thermal-admittance spectroscopy measurements, are powerful tools to obtain important parameters of the solar cell, such as doping and defect densities, built-in voltages, and activation energies.

However, the validity of these analyses assumes that the capacitance response originates solely from the absorber layer.

Here, the authors demonstrate that this assumption is not valid for perovskite solar cells, since the thin and low-mobility selective-contact layers significantly contribute to the measured capacitance. Using a combination of drift-diffusion simulations and analytical modeling, they develop guidelines for the measurement of doping and defect densities, built-in voltages, and activation energies from these capacitance methods. These guidelines can be applied to any photovoltaic technology that incorporates low-conductivity charge-transport layers in addition to the absorber layer.

Simulation with ions was performed using Setfos.

Maki Hiraoka, Nobuyuki Ishida, Akio Matsushita, Ryusuke Uchida, Takeyuki Sekimoto, Teruaki Yamamoto, Taisuke Matsui, Yukihiro Kaneko, Kenjiro Miyano, Masatoshi Yanagida, and Yasuhiro Shirai

CS Appl. Energy Mater. 2022, 5, 4, 4232–4239

doi/10.1021/acsaem.1c03747

Kelvin probe force microscopy has been employed to monitor the cross-sectional potential profile in lead-halide perovskite photovoltaic cells. From systematic investigations on many devices under varying bias voltage and light illumination conditions, we are able to deduce quantitative profile features with low noise that allows us to compare the local electronic properties in the working devices against numerical calculations.

The research team applied this technique to devices before and after degradation. Through the profile change before and after, we located the degraded components and inferred the source of the loss of the performance.

Setfos was used to simulate the photovoltaic actions of the device.

Camilla Vael, Sandra Jenatsch, Simon Züfle, Frank Nüesch, and Beat Ruhstaller

Journal of Applied Physics 131, 205702 (2022)

doi.org/10.1063/5.0088426

Simplified physical models are insufficient to describe the transient current after thermal stimulation in organic semiconductors. This is a recent finding from the group of Beat Ruhstaller. Drift-diffusion simulations obtained with the simulation software Setfos revealed the shortcomings of the physical models.

Simulations modeling is more powerful than analytical approaches for the interpretation of experimental data by accounting for non-ideal properties like exciton splitting and non-homogenous trap densities.

Tom P. A. van der Pol, Kunal Datta, Martijn M. Wienk, and René A. J. Janssen

Adv. Optical Mater. 2022, 2102557

doi.org/10.1002/adom.202102557

Photoluminescence (PL) helps you determine material properties and dynamic effects in #perovskite devices. But it is not easy to interpret PL spectra of #perovskites and get to the intrinsic material properties. This work is showing you how to do it.

The group of Prof. Rene Janssen at the Eindhoven University of Technology developed an optical model to quantify the intrinsic PL of a perovskite film and determine the influence of the extrinsic factors on the measured PL. The model is based on film thickness, refractive index, extinction coefficient, and carrier diffusion length as input parameters. The authors concluded that the largest mismatch between intrinsic and measured PL is observed for materials with a long diffusion length (>0.5um) and a layer thickness of >300nm.

The simulation software Setfos was instrumental in calculating an accurate emission spectrum to quantify the intrinsic PL for the perovskite. The simulation uses the real nk spectra of the materials and layer thickness as an input, which is the key to resolving the optical system.

The description you find in this paper can be used as a protocol to analyze your PL data on perovskite films.

Brinkmann, K.O., Becker, T., Zimmermann, F. et al.

Nature 604, 280–286 (2022).

doi.org/10.1038/s41586-022-04455-0

In this Nature paper the research team reached a new outstanding certified efficiency record of 23.1% with a two-terminal perovskite/organic solar cell.

Thanks to an ALD-deposited InOx interconnection layer, the current between the two subcells is perfectly matched at 14.1 mA/cm2. The high Voc of 2.15 V indicates an almost ideal interconnection between the two subcells.

These devices are using an organic absorber for the narrow-gap subcell, which doesn’t need the high-temperature processing of silicon and is more stable than the commonly used narrow-bandgap perovskites based on Sn.

With the software Setfos from FLUXiM AG, they carried out optical simulations to identify the wide bandgap perovskite that matches the organic subcell.

Dario Di Carlo Rasi, Koen H. Hendriks, Martijn M. Wienk, and René A. J. Janssen

Advanced Materials, 2018, 1803836

https://doi.org/10.1002/adma.201803836

Abstract:

A monolithic two-terminal solution-processed quadruple junction polymer solar cell in an n–i–p (inverted) configuration with four complementary polymer: fullerene active bulk-heterojunction layers is presented. The subcells possess different optical bandgaps ranging from 1.90 to 1.13 eV. Optical modeling using the transfer matrix formalism enables the prediction of the fraction of absorbed photons from sunlight in each subcell and determines the optimal combination of layer thicknesses. The quadruple junction cell features an open-circuit voltage of 2.45 V and has a power conversion efficiency of 7.6%, only slightly less than the modeled value of 8.2%. The external quantum efficiency spectrum, determined with appropriate light and voltage bias conditions, exhibits, in general, an excellent agreement with modeled spectrum. The device performance is presently limited by bimolecular recombination, which prevents using thick photoactive layers that could absorb light more efficiently.

Sheng Bi, Zhongliang Ouyang, Shoieb Shaik and Dawen Li

Scientific Reports 8, 9574 (2018)

https://doi.org/10.1038/s41598-018-27868-2

S. Altazin, C. Kirsch, E. Knapp, A. Stous, and B. Ruhstaller

Journal of Applied Physics 124, 135501 (2018)

https://doi.org/10.1063/1.5043245

Abstract: We present a new approach to simulate the transport of charges across organic/organic layer interfaces in organic semiconductor devices. This approach combines the drift-diffusion formalism away from the interface with a hopping description of the charge transport in the vicinity of the interface. It has been implemented in the commercial software SETFOS allowing for fast simulations of the complete device. This new model takes into account both recombination and generation mechanisms across the interface enabling the modeling of charge-generation/recombination interfaces for the numerical simulation of tandem devices. Using this approach, it is also possible to simulate devices using 1,4,5,8,9,11-Hexaazatriphenylenehexacarbonitrile as a hole-injection layer. This particular material has a very deep HOMO level (approximately 9.5 eV), which would seemingly prevent such a layer to be used as a hole-injection material in the framework of traditional drift-diffusion models.

Taesoo Kim, Yuliar Firdaus, Ahmad R. Kirmani, Ru-Ze Liang, Hanlin Hu, Mengxia Liu, Abdulrahman El Labban, Sjoerd Hoogland, Pierre M. Beaujuge, Edward H. Sargent, and Aram Amassian

ACS Energy Letters 3, 1307 (2018)

https://doi.org/10.1021/acsenergylett.8b00460

Francisco Peña-Camargo, Jarla Thiesbrummel, Hannes Hempel, Artem Musiienko, Vincent M. Le Corre, Jonas Diekmann, Jonathan Warby, Thomas Unold, Felix Lang, Dieter Neher, Martin Stolterfoht;

Applied Physics Reviews 1 June 2022; 9 (2): 021409. 86

https://doi.org/10.1063/5.00852

This scientific article presents a multifaceted approach to determine the electronic doping density in metal-halide perovskite systems. The researchers used various optical and electrical characterization techniques to quantify the doping density. The results showed that the doping density in perovskite thin films is below the critical threshold that would affect device performance. The doping-induced charges were found to be too low to redistribute the built-in voltage in the perovskite active layer. However, the presence of mobile ions in sufficient quantities was observed, which could create space-charge regions in the active layer. The experimental results were supported by drift-diffusion simulations. The findings suggest that perovskite thin films behave as intrinsic semiconductors and that doping does not significantly influence the performance of devices based on these materials.

How was Setfos used

Setfos was used to check that findings for doping also holds for mobile ions.

F. Ventsch, M.C. Gather, K. Meerholz

Organic Electronics 11, 57 (2010)

https://dx.doi.org/10.1016/j.orgel.2009.09.026

S. Hamwi, J. Meyer, M. Kröger, T. Winkler, M. Witte, T. Riedl, A. Kahn, W. Kowalsky

Advanced Functional Materials 20,1762 (2010)

https://dx.doi.org/10.1002/adfm.201000301

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M. Mazzeo, F. Della Sala, F. Mariano, G. Melcarne, Y. Duan, S. D'Agostino , R. Cingolani, G. Gigli

Advanced Materials, 22, 4696-4700, 2010

https://doi.org/10.1002/adma.201001631

R. Mauer, I.A. Howard, F. Laquai

Journal of Physical Chemistry Letters, 1, 3500-3505, 2010

https://dx.doi.org/10.1021/jz101458y

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G. Xie, Z. Zhang, Q. Xue, S. Zhang, L. Zhao, Y. Luo, P. Chen, B. Quan, Y. Zhao, S. Liu

Organic Electronics 11, 2055, 2010

https://dx.doi.org/10.1016/j.orgel.2010.10.001

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E. Knapp, R. Häusermann, H.U. Schwarzenbach, B. Ruhstaller

Journal of Applied Physics, 108, 054504-0545012, 2010

https://dx.doi.org/10.1063/1.3475505

B. Perucco, N.A. Reinke, D. Rezzonico, M. Moos, and B. Ruhstaller

Optics Express, 18 (S2), A246-A260, 2010

https://doi.org/10.1364/OE.18.00A246

B. Perucco, N.A. Reinke, F. Müller, D. Rezzonico, and B. Ruhstaller

Proc. SPIE 7722, Organic Photonics IV, 77220F (2010)

https://doi.org/10.1117/12.853989

G. Cheng, M. Mazzeo, S. D’Agostino, F. Della Sala, S. Carallo, G. Gigli

Optics Letters, 35 (5), 616-618, 2010

https://doi.org/10.1364/OL.35.000616

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P.M. Boland, T. Abdel-Fattah, H. Baumgart, G. Namkoong

2009 International Semiconductor Device Research Symposium, 2009

https://doi.org/10.1109/ISDRS.2009.5378124