Efficient and stable TiO2 nanorod array structured perovskite solar cells in air: Co-passivation and synergistic mechanism

In recent years, single crystal TiO2 nanorod arrays (TNRAs) with fewer grain boundaries for photo-generated electron transport and ordered channel structures for perovskite filling have been employed as electron transport layers for efficient perovskite solar cells (PSCs). However, further improvements in TNRA-based PSC performance are urgently needed because defects in the perovskite layer seriously hinder device efficiency and stability. In this study, with TNRAs as the electron transport layer, CH3NH3PbI3 (MAPbI(3)) perovskite films were prepared in air by a two-step spin coating method. The grain boundary defects and surface defects of the MAPbI(3) layer are co-passivated by octyl ammonium iodide (CH3(CH2)(7)NH3I, OAI) and choline chloride (HOCH2CH2N (CH3)(3)Cl, Ch), respectively, and the effects of the two passive materials on the power conversion efficiency (PCE) and stability of TNRA-based PSCs are systematically investigated. The results reveal that the introduction of OAI facilitates the formation of intermolecular valence bonds between crystalline MAPbI(3) to enhance its structural stability, while Ch passivates the Pb-I antisite substitution defect and I- vacancy defect on the perovskite film surface. Compared with the pristine device, the optimal PCE of the passivated device increases from 18.86% to 20.08%, and the thermal, humid and long-term stability of the device is also improved.

Automated summary

This study investigates the effects of octyl ammonium iodide (OAI) and choline chloride (Ch) on the performance and stability of titanium dioxide nanorod arrays (TNRAs)-based perovskite solar cells (PSCs). The results show that OAI enhances the structural stability of the perovskite layer, while Ch passivates defects on the surface. The optimized devices with the passivated layers achieve higher power conversion efficiency (PCE) and improved stability compared to the pristine devices.