Heterogeneous FASnI3 Absorber with Enhanced Electric Field for High-Performance Lead-Free Perovskite Solar Cells

• Published in: Nano-micro letters Vol. 14; no. 1; pp. 99 - 14
• Main Authors: Wu, Tianhao, Liu, Xiao, Luo, Xinhui, Segawa, Hiroshi, Tong, Guoqing, Zhang, Yiqiang, Ono, Luis K., Qi, Yabing, Han, Liyuan
• Format: Journal Article
• Language: English
• Published: Singapore Springer Nature Singapore 08.04.2022; Springer Nature B.V; Springer Singapore; SpringerOpen
• Subjects: Absorbers; Built-in electric field; Bulk charge recombination; Efficiency; Electric fields; Engineering; Gradient FASnI3 absorber; Illumination; Lead free; Lead-free perovskite solar cell; Lewis base; Nanoscale Science and Technology; Nanotechnology; Nanotechnology and Microengineering; Open circuit voltage; Perovskite Solar Cells; Perovskites; Photoelectrons; Photovoltaic cells; Recrystallization; Solar cells; Tin; absorber; Bulk charge recombination; Gradient FASnI; Built-in electric field; Lead-free perovskite solar cell
• ISSN: 2311-6706; 2150-5551; 2150-5551
• DOI: 10.1007/s40820-022-00842-4

Highlights A novel strategy to further improve the efficiency of lead-free tin perovskite solar cells by carefully controlling the built-in electric field in the absorber is described. A promising efficiency of 13.82% was obtained based on the formamidinium tin iodide (FASnI 3 ) perovskite solar cells with a vertical Sn 2+ gradient and an enhanced electric field. The solar cell with a heterogeneous FASnI 3 absorber is ultrastable, maintaining over 13% efficiency after operation under 1-sun illumination for 1,000 h in air. Lead-free tin perovskite solar cells (PSCs) have undergone rapid development in recent years and are regarded as a promising eco-friendly photovoltaic technology. However, a strategy to suppress charge recombination via a built-in electric field inside a tin perovskite crystal is still lacking. In the present study, a formamidinium tin iodide (FASnI 3 ) perovskite absorber with a vertical Sn 2+ gradient was fabricated using a Lewis base-assisted recrystallization method to enhance the built-in electric field and minimize the bulk recombination loss inside the tin perovskites. Depth-dependent X-ray photoelectron spectroscopy revealed that the Fermi level upshifts with an increase in Sn 2+ content from the bottom to the top in this heterogeneous FASnI 3 film, which generates an additional electric field to prevent the trapping of photo-induced electrons and holes. Consequently, the Sn 2+ -gradient FASnI 3 absorber exhibits a promising efficiency of 13.82% for inverted tin PSCs with an open-circuit voltage increase of 130 mV, and the optimized cell maintains over 13% efficiency after continuous operation under 1-sun illumination for 1,000 h.