Enhanced efficiency of organic solar cells by using a ZnO-Fe2O3 electron transport layer

In this study, a ZnO-Fe 2 O 3 thin film was designed as electron transport layer for organic solar cells (OSCs). The preparation strategy was based on the spin coating of aqueous sol–gel precursor. The result showed that composite ZnO-Fe 2 O 3 -based OSCs had higher power conversion efficiency than pure ZnO-based OSCs. To explain this result, morphology, optical and physical properties of ZnO-Fe 2 O 3 were investigated to analyze the relation between structure of interface layer and performance of OSCs. It was demonstrated that composite ZnO-Fe 2 O 3 layer had denser structure and lower surface roughness than pure ZnO layer. Thus, it showed a good contact with the active layer. Furthermore, 3.3% Fe 2 O 3 could reduce the W F and E g of ZnO, and greatly enhanced electron mobility from the acceptor (IT-4F) phase to the ZnO/ITO electrode. Meanwhile, ZnO-Fe 2 O 3 layer showed a low reflectivity that allowed more photons to entrance the active layer for utilization. Hence, the higher short-circuit current and power conversion efficiency were achieved in ZnO-Fe 2 O 3 -based OSCs. Graphical abstract