CH3NH3PbI3 grain growth and interfacial properties in meso-structured perovskite solar cells fabricated by two-step deposition

Zhibo Yao; Wenli Wang; Heping Shen; Ye Zhang; Qiang Luo; Xuewen Yin; Xuezeng Dai; Jianbao Li; Hong Lin

doi:10.1080/14686996.2017.1298974

CH₃NH₃PbI₃ grain growth and interfacial properties in meso-structured perovskite solar cells fabricated by two-step deposition

Sci Technol Adv Mater. 2017 Apr 10;18(1):253-262. doi: 10.1080/14686996.2017.1298974. eCollection 2017.

Authors

Zhibo Yao¹, Wenli Wang², Heping Shen¹, Ye Zhang¹, Qiang Luo¹, Xuewen Yin¹, Xuezeng Dai¹, Jianbao Li^{3

1}, Hong Lin¹

Affiliations

¹ State Key Laboratory of New Ceramics & Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing, PR China.
² National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, PR China.
³ State Key Laboratory of Marine Resource Utilization in South China Sea, Materials and Chemical Engineering Institute, Hainan University, Haikou, PR China.

Abstract

Although the two-step deposition (TSD) method is widely adopted for the high performance perovskite solar cells (PSCs), the CH₃NH₃PbI₃ perovskite crystal growth mechanism during the TSD process and the photo-generated charge recombination dynamics in the mesoporous-TiO₂ (mp-TiO₂)/CH₃NH₃PbI₃/hole transporting material (HTM) system remains unexploited. Herein, we modified the concentration of PbI₂ (C_(PbI2)) solution to control the perovskite crystal properties, and observed an abnormal CH₃NH₃PbI₃ grain growth phenomenon atop mesoporous TiO₂ film. To illustrate this abnormal grain growth mechanism, we propose that a grain ripening process is taking place during the transformation from PbI₂ to CH₃NH₃PbI₃, and discuss the PbI₂ nuclei morphology, perovskite grain growing stage, as well as Pb:I atomic ratio difference among CH₃NH₃PbI₃ grains with different morphology. These C_(PbI2)-dependent perovskite morphologies resulted in varied charge carrier transfer properties throughout the mp-TiO₂/CH₃NH₃PbI₃/HTM hybrid, as illustrated by photoluminescence measurement. Furthermore, the effect of CH₃NH₃PbI₃ morphology on light absorption and interfacial properties is investigated and correlated with the photovoltaic performance of PSCs.

Keywords: 209 Solar cell / Photovoltaics; 302 Crystallization / Heat treatment / Crystal growth; 50 Energy Materials; CH3NH3PbI3 grain growth; Perovskite solar cell; concentration of PbI2; interfacial property; two-step deposition.