Efficient and Stable Tin Perovskite Solar Cells by Introducing Π-conjugated Lewis Base
Tianhao Wu a, Xiao Liu b, Liyuan Han a b
a Shanghai Jiao Tong University, 800 Dongchuan Road, Minhang District, Shanghai, China, Shanghai, 201100, China
b National Institute for Materials Science (NIMS), Center for Green Research on Energy and Environmental Materials, Photovoltaic Materials Group, Japan, Japan
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP20)
Tsukuba-shi, Japan, 2020 January 20th - 22nd
Organizers: Michio Kondo and Takurou Murakami
Oral, Xiao Liu, presentation 065
DOI: https://doi.org/10.29363/nanoge.iperop.2020.065
Publication date: 14th October 2019

Tin perovskite solar cells (TPSCs) as the most promising candidate for lead-free PSCs have attracted much attention all over the world. However, tin perovskite films deposited by the solution-based strategy usually undergo a much faster crystallization rate than that of the lead analogs,[1] which leads to abundant pinholes and random crystal orientation that induce serious charge recombination and poor device performance.[2] Besides, tin perovskite materials show poor environmental stability, they easily undergo phase transition or oxidization process when exposed to the air. Additive engineering is a promising way to improve both the film quality and stability, but there is a lack of design principle for the additive molecules to further improve the efficiency and long-term stability of TPSCs.

In this manuscript, we introduced the additive molecules designed with a π-conjugated unit and Lewis base functional groups to govern the crystallization kinetics of FASnI3 perovskite.[3] It's found that the π-conjugated units with strong electron-donating ability significantly increase the electron density of Lewis base groups, resulting in more stable intermediate phase formed with the Lewis acid Sn2+ components, leading to a compact and uniform perovskite film with much longer carrier recombination lifetime. Moreover, the hydrophobic nature of π-conjugated system also retards the permeation of moisture into perovskite crystal and therefore prevents the degradation of FASnI3 film in air.

As a result, we achieved a stabilizing power conversion efficiency of 10.1% for the TPSCs, and a certified steady-state efficiency of 9.2% was also obtained from the accredited test center, National Institute of Advanced Industrial Science and Technology (AIST, Japan). In addition, the TPSCs treated with CDTA maintained over 90% of its initial PCE after 1000-hours light soaking in air.

We acknowledge the grants from the New Energy and Industrial Technology Development Organization (NEDO, Japan), and the KAKEHI Grant of Japan.

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