2nd VIPERLAB workshop on Peroskite Solar Cells Characterization

Dr. Natalia Maticuc, technical manager of HZB VIPERLAB, presents the project, its main goals and objectives to accelerate the development of perovskite photovoltaics in Europe by fostering collaborations between academia and industry, as well as facilitating and coordinating access to the best EU-based perovskite research infrastructures thanks to its 3 main pillars of activities:

1. Access to expertise and infrastructure:
2. Networking and Training Actions:
3. Develop infrastructure and knowledge-base:

By this pesentation it will given  a short argumentation, why harmonization and standards are critical for ensuring the quality, safety and interoperability of any PV technology in order to drive its adoption and success on a global scale. Efficiencies of lab-scale perovskite single junction devices as well as perovskite/ Si tandems are (more than) competitive. As a next step, scaled modules that meet the safety and performance standards have to be developed and tested in the field. TThe presentations outline how to get there and how the VIPERLAB project tries to accelerate the successful realization of these needed actions.   

In this presentation, Dr. Martin Schubert discusses details about precise measurements of perovskite-silicon tandem solar cell performance. Details about quantum efficiency measurements and I-V measurements are given. The benefit of full area bias light during quantum efficiency measurements is demonstrated and the importance of carefully adjusting the spectrum for I-V measurements to the solar cell under test is explained. Finally the calibration procedure for perovskite-silicon tandem cells is described.

In the presentation Dr. Christian Wolff discusses tandem solar cells in a 2T configuration, i.e. two cells connected in series with complementary bandgaps. Based on electrical simulations using a simple two-diode model (with reasonable parameters for the experimental set). Christian discusses the impact of the discrepancy and how it affects the JV characteristics of a tandem device, particularly looking at the very different "qualities" of the subcells. Simulations and experiments are compared, with reasonable agreement. Finally he discusses their methods for measuring these cells by combining EQE, JV and mismatch measurements, before pointing to new effects, and points out that as a community we need to be careful during the characterization (meta-stability during measurement, luminescent coupling) in the near future

With the rapid development of perovskite solar cells (PSCs) efficiency and stability, the questions of their real-world operation come to the forefront. In this talk, Dr. Mark Khenkin shares the insights of working with perovskite-based devices in the HZB test field located in Berlin, Germany. With the help of a special setup performing continuous MPP tracking on research-size cells (1 cm² or less), they  were able to accumulate some of the longest outdoor datasets with perovskite-based devices, some surpassing two years. This not only enables discussion of stability topics but also allows analysis of the impacts of environmental factors and seasonal effects on cells' performance. One of the most important lessons learned is the dramatic influence of meta-stability on the outdoor performance of perovskite cells. It significantly complicates parameters' extraction from the data and can result in large artefacts if ignored. Even if accounted for, it does lead to non-negligible losses in the energy yield and affects the cell's long-term outdoor stability. Mark  also discusses in this talk their outlook on some of the important open questions in the field of outdoor testing of perovskite-based devices.

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During the presentation Dr. Natalia Maticiuc, VIPERLAB Project Technical manager presents the Research infrastructures offered by VIPERLAB for material synthesis,  device design and development, standardized testing methods, simulation methods and modelling. Particularly Dr. Maticiuc highlights the infrastructures offered by our project for the Single/Tandem junction solar cells characterization, and the electrical and optical analyses of perovskite silicon tandem cells.