Rare earth cation doped SnO2 ETL for the reduction of energy level mismatch of the highly efficient perovskite solar cells
Shamim Ahmmed a b, He Yulu a b, Kiyoto Matsuishi b, Md. Emrul Kayesh a, Ashraful Islam a
a Photovoltaic Materials Group, Center for Green Research on Energy and Environmental Materials, National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba 305-0047, Ibaraki, Japan
b Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573, Ibaraki, Japan
Poster, Shamim Ahmmed, 076
Publication date: 24th October 2023

Perovskite solar cells (PSCs) have attracted much attention because of the fast progress of their power conversion efficiency (PCE) has reached from an initial 3.8% to 26.1% within 14 years.1 The highly efficient perovskite solar cells mostly utilize the SnO2 electron transport layer (ETL) because of its excellent optical and electrical properties.2,3 However, high conduction band offset (CBO) at SnO2/perovskite interface and high oxygen vacancy on the SnO2 surface cause the open circuit voltage (VOC) loss due to the higher recombination velocity at the SnO2/perovskite interface.4,5 From the theoretical analysis, Duan et al. showed that the conduction band (CB) of the SnO2 can be shifted to upward energy level with the p-type doping.6 In this research, we introduced a rare earth cation into SnO2 as a p-type dopant to overcome the limitations of the SnO2 ETL in the practical PSCs. From the X-ray photoelectron spectroscopy (XPS) analysis, it was found that the oxygen vacancy on the SnO2 surface was reduced after introduction of doping element. We confirmed the reduction of CBO at SnO2/perovskite interface from the ultraviolet photoelectron spectroscopy (UPS) and optical measurements. As a result, the doped SnO2 ETL in PSCs enhanced the VOC by around 100 mV compared to the pristine SnO2 ETL. Finally, we observed the PCE of 21.02% from the doped SnO2 ETL-based PSCs with high stability, while pristine SnO2 ETL-based PSCs showed a PCE of 19.25%.

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