Interfacial Engineering for Efficient Low-Temperature Flexible Perovskite Solar Cells

Photovoltaic technology with low weight, high specific power in cold environments, and compatibility with flexible fabrication is highly desired for near-space vehicles and polar region applications. Herein, we demonstrate efficient low-temperature flexible perovskite solar cells by improving the interfacial contact between electron-transport layer (ETL) and perovskite layer. We find that the adsorbed oxygen active sites and oxygen vacancies of flexible tin oxide (SnO2) ETL layer can be effectively decreased by incorporating a trace amount of titanium tetrachloride (TiCl4). The effective defects elimination at the interfacial increases the electron mobility of flexible SnO2 layer, regulates band alignment at the perovskite/SnO2 interface, induces larger perovskite crystal growth, and improves charge collection efficiency in a complete solar cell. Correspondingly, the improved interfacial contact transforms into high-performance solar cells under one-sun illumination (AM 1.5G) with efficiencies up to 23.7 % at 218 K, which might open up a new era of application of this emerging flexible photovoltaic technology to low-temperature environments such as near-space and polar regions. In this study, a high-quality SnO2 layer with decreased adsorbed oxygen (Ochem) active sites and oxygen vacancies (Ovac) was fabricated on a flexible substrate by introducing TiCl4 into the SnO2 bulk layer. The first evidence of flexible perovskite cells working at low temperature was demonstrated, with efficiency as high as 23.7 % based on an improved SnO2 layer.+image

Automated summary

This study demonstrates efficient low-temperature flexible perovskite solar cells by improving the interfacial contact between the electron-transport layer (ETL) and the perovskite layer. The incorporation of titanium tetrachloride (TiCl4) effectively decreases the adsorbed oxygen active sites and oxygen vacancies of the flexible tin oxide (SnO2) ETL layer. This leads to improved charge collection efficiency and higher solar cell efficiencies up to 23.7% at 218 K, opening up new possibilities for flexible photovoltaic technology in low-temperature environments.