Preparation of High-Efficiency (>14%) HTL-Free Carbon-Based All-Inorganic Perovskite Solar Cells by Passivation with PABr Derivatives

Due to the advantages of low cost and good thermal stability, all-inorganic CsPbI 2 Br carbon-based perovskite solar cells (C-PSCs) without a hole transport layer have been rapidly developed in recent years. While the carbon electrode is in direct contact with the CsPbI 2 Br film, higher requirements are placed on the defects and energy level arrangement of the CsPbI 2 Br layer, which leads to the relatively low photoelectric conversion efficiency (PCE) of C-PSCs. Herein, propylamine hydrobromide (PABr) and its derivative 3-bromopropylamine hydrobromide (3Br-PABr) were used to passivate the surface defects of CsPbI 2 Br C-PSCs for the first time. The results show that passivation molecules are modulated by the substituent effect, leading to a stronger interaction between amino groups and uncoordinated Pb 2+ ions, which facilitates a better passivation effect of 3Br-PABr. In addition, 3Br-PABr promotes the gradient arrangement of energy levels while passivating surface defects, which accelerates the rapid extraction of holes. After the passivation by PABr and 3Br-PABr, the PCE of HTL-free CsPbI 2 Br C-PSCs increased from 12.15% for the control device to 13.15 and 14.04%, respectively, which are among the highest reported values of CsPbI 2 Br C-PSCs.