Inverted CsPbI2Br perovskite solar cells with enhanced efficiency and stability in ambient atmosphere via formamidinium incorporation

• Published in: Solar energy materials and solar cells 2020-12, Vol.218, p.110741, Article 110741
• Main Authors: Chen, Mengmeng, Sahamir, Shahrir R., Kapil, Gaurav, Baranwal, Ajay K., Kamarudin, Muhammad Akmal, Zhang, Yaohong, Nishimura, Kohei, Ding, Chao, Liu, Dong, Hirotani, Daisuke, Shen, Qing, Hayase, Shuzi
• Format: Article
• Language: English
• Subjects: Atmosphere; Cations; Circuits; Cs1−xFAxPbI2Br solar cell; CsPbI2Br solar Cell; Energy conversion efficiency; Fabrication; Open circuit voltage; Perovskites; Phase stability; Photovoltaic cells; Photovoltaics; Solar cells; Stability; Wide-bandgap
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2020.110741

CsPbI2Br is one of candidates of the top layer for the all perovskite tandem solar cells. However, the perovskite is prone to change the phase from α (black) to δ (yellow) type. In this research, Cs1-xFAxPbI2Br perovskites were fabricated in an ambient atmosphere, and their properties immediately after the fabrication and the phase stability were investigated. The quality of the perovskite films was enhanced and the trap density was reduced after the incorporation of the FA cations. The phase stability of the Cs1-xFAxPbI2Br perovskite was effectively enhanced. Consequently, the highest power conversion efficiency of 12.28% with open-circuit voltage (Voc) of 1.09 V, current intensity (Jsc) of 15.65 mA cm−2, and fill factor of 72% in the planar solar cell based on Cs0.7FA0.3PbI2Br perovskite is reported. The bandgap was optimized to be about 1.82 eV suitable for all perovskite tandem top layer. Most importantly, all the photovoltaic parameters of Cs0.7FA0.3PbI2Br perovskite solar cells showed ignorable decay after 2 months’ measurement in an ambient atmosphere with the presence of air and humidity without encapsulation. •Detailed analysis to study the phase stability of CsPbI2Br by the introduction of FA+ cation into the crystal lattice.•A 100% internal quantum efficiency (IQE) was demonstrated in comparison to reference CsPbI2Br (IQE~60%) based solar cells.•Bandgap engineering of CsxFA1-xPbI2Br combined with NiOx led to a highly efficient 12.28% solar cell.•An excellent ambient air-stability of 2 months for the un-encapsulated solar cell was achieved.