Charge transport study of perovskite solar cells through constructing electron transport channels

Perovskite solar cells (PSC) have attracted much attention in the recent years. It is important to understand their working principle in order to uncover the reasons behind their high efficiency. In this study, the carrier transport mechanism of PSC by controlling the structure of a scaffold is investigated. CeO₂ is used as an electron blocking material in PSCs to study the electron transport behavior for the first time. The influence of light absorption can be excluded because CeO₂ has a similar bandgap to TiO₂. A variety of scaffolds are constructed using nano-TiO₂ and CeO₂. The results show that electrons can transport from light absober (perovskite) to FTO electrode (external circuit) through two kinds of channels. The energy band level, as well as the electronic conductivity of the scaffolds, is are key issues that affect electron transport. Although perovskites are able to transport both electrons and holes, it is still necessary to have effective electron transport channels (ETCs) between perovskite and external circuit for the sake of high efficiency. Electrochemical impedance spectroscopy analysis suggests that the lack of such channels will result in high recombination. The number of ETCs and effecient electron-hole separation are also proven to be important for cell performance.