Proceedings Article | 1 October 2023
KEYWORDS: Perovskite, Solar cells, Electrical conductivity, Thin film solar cells, Passivation, Lithium, Interfaces, Thin films, Photovoltaics, Ions
Charge-selective interlayers are crucial in thin-film photovoltaics, such as organic and perovskite solar cells (PSCs). Doped and undoped charge transport layers (CTLs) constitute perhaps the most important class of charge-selective interlayers; however, it is not well understood how a CTL should be designed in order to ensure efficient extraction of majority carriers while blocking minority carriers.
This work clarifies how well CTLs with varying majority carrier conductivities block minority carriers. We use the charge extraction by linearly increasing voltage (CELIV) technique to determine the surface recombination velocity of minority carriers in model PSC devices with varying majority carrier conductivity in the transport layer [1]. Our results show that CTLs with high conductivity for majority carriers do not block minority carriers – at least not at operating voltages close to or above the built-in voltage – due to direct bimolecular recombination across the CTL/absorber interface. We furthermore discuss and propose design principles to achieve selective charge extraction in thin film solar cells using CTLs.
Another important factor is the stabilizing effect of the PSC degradation through passivating the interface between CTLs and the perovskite absorber. We introduced a thin crosslinked PC61BM layer on top of the SnO2 electron transport layer, resulting in immobilization of Li+ ions. This resulted in the elimination of the “burn-in” degradation, showing for the first time a zero “burn-in” loss in the performances while boosting the device efficiency to > 22% for triple-cation based PSCs and > 24% for formamidinium based (FAPbI3) PSCs, proving the general validity of our approach and creating a new framework for the realization of stable PSCs devices [2].
[1] Mathias Nyman, Christian Ahläng, Staffan Dahlström, Manasi Pranav, Johannes Benduhn, Syeda Qudsia, Jan-Henrik Smått, Donato Spoltore, and Ronald Österbacka, submitted
[2] Changzeng Ding, Li Yin, Jinlong Wang, Valentina Larini, Lianping Zhang, Rong Huang, Mathias Nyman, Liyi Zhao, Chun Zhao, Weishi Li, Qun Luo,Yanbin Shen, Ronald Österbacka, Giulia Grancini*, Chang-Qi Ma*, “Boosting Perovskite Solar Cells Efficiency and Stability: Interfacial Passivation of Crosslinked Fullerene Eliminates the “burn-in” Decay”, Advanced Materials 35, 2207656 (2023)
