Reducing recombination losses in perovskite solar cells

• Applicant: Dr. Kristofer Tvingstedt, Ph.D.
• Subject Area: Experimental Condensed Matter Physics ; Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 382633022

Perovskite based photovoltaics are currently emerging as a potential alternative route to inexpensively convert solar energy into electricity due to recent encouraging progress in the field. In particular, perovskite solar cells are expected to be very cost-effective as they, just like organic solar cells, can be easily processed from solution, which enables manufacturing via simple printing techniques. Very low cost of production is hence envisaged, but like for any PV technology, high power conversion efficiency as well as stability is paramount for making devices attractive for the market. To reach this well warranted goal, a much better understanding of the current principal limitations is urgently needed. In very general terms, two prominent causes for power conversion efficiency limitations of photovoltaics exist: first, the material absorption width and strength, leading to limited spectral sunlight coverage and current generation, and second, the electrical losses, i.e. recombination of charge carriers within the devices, after absorption has taken place, that mainly limits the photovoltage of the device. Leaving the task of optimizing the material absorption to the synthetic chemists, our main aim within this project is to reveal and minimize the dominant carrier recombination limitations of completed perovskite based solar cells, essential for further increase of power conversion efficiency.By combining complementary experiments on radiative and non-radiative recombination dynamics in perovskite solar cells, under transient as well as steady and quasi steady state conditions, we will here aim to establish a more comprehensive picture of the detailed loss mechanisms, both qualitatively and quantitatively. By comparing the behavior of different charge selective materials and perovskite layer preparation conditions, correlating our experimental results with rate modelling approaches, we aim to gain essential information concerning the origin of the dominant recombination mechanisms. We particularly aim to clarify the influence of surface recombination losses at the interfaces and how to also minimize these. All in all, the results of this project should allow providing detailed feedback to both material synthesis and device manufacturing in view of optimizing the performance of this new and extremely promising photovoltaic technology.

• DFG Programme: Research Grants
• International Connection: Spain, United Kingdom
• Cooperation Partners: Professor Dr. Henk J. Bolink; Dr. Michele Sessolo, Ph.D.; Professor Dr. Henry Snaith, Ph.D.