Lithium chloride-based interface engineering at electron transport and perovskite layers to boost the performance of perovskite photovoltaics

During the past decade in the perovskite solar cells (PSCs) field, mesoporous titanium oxide (mp-TiO2) has been widely used as electron transport layers (ETLs) to promote the electron extraction process and also as a scaffold for the perovskite layer (PSK) to gain better PSC performance. Usually, the interface between the mp-TiO2 layer and PSK needs a modification process to boost the performance of mp-TiO2-based PSCs. Here, lithium chloride (LiCl) was used to modify the ETL/PSK interface. Results showed that a simple interface engineering based on LiCl could improve the morphology and crystalline properties of the PSK film, and motivate charge transport processes at the ETL/PSK interface and within PSK due to lower grain boundaries in PSK. Overall, ETL interface engineering with a 0.03 M LiCl solution leads to an efficiency of 11.24% for PSCs, higher than that of 7.42% for control devices. In addition, the modified PSCs compared to control PSCs were more stable in an environment with a humidity of 25%. The improved stability is caused by reduced GBs and a suppressed lead iodide (PbI2) surplus in the modified PSK.