Sandwich-like electron transporting layer to achieve highly efficient perovskite solar cells

摘要

Passivating the carrier recombination at the heterojunction interface and improving the efficiency of charge separation are effective means to boost the performance of perovskite solar cells (PSCs). The interface modification between the anode and the electron transporting layer (ETL) or constructing bilayer structural ETLs has been proved to be the effective way to achieve high-efficient charge extraction and collection. Combining the advantages of both techniques might further achieve lower energy loss and higher efficiency in PSCs. Herein, we design a sandwich-like SnO2-CQDs-SnO2 (S-C-S) ETLs, i.e. an ultrathin band-gap tunable carbon quantum dots (CQDs) layer is inserted between ultrathin SnO2 bottom layer and SnO2 top layer. The bottom ultrathin SnO2 layer passivates the defects of SnO2:F (FTO) and reduces the carrier recombination at the FTO/ETLs interface. The CQDs layer enhances the optical transmission of ETLs, accelerates carrier transport process and improves the hole-blocking ability. Such S-C-S ETLs greatly enhance the power conversion efficiency (PCE) of PSCs and eliminate hysteresis to the maximum extent. This work provides a new concept for designing novel electronic transmission materials for solar cells, and lays the foundation for further achieving higher PCE in PSCs.