High efficiency inverted polymer solar cells with room-temperature titanium oxide/polyethylenimine films as electron transport layers

PTB7:PC71BM inverted polymer solar cells with a room-temperature TiOx/PEI electron transport layer achieve an average power conversion efficiency of 8.72% (the champion power conversion efficiency is 9.08%), which is much better than that of the control devices based on PEI (7.00%) or TiOx (7.38%). The room-temperature TiOx/PEI layer exhibits outstanding capacities, including increased electron mobility, reduced series resistance and improved electron extraction at the cathode interface.