Spray deposited lanthanum doped TiO2 compact layers as electron selective contact for perovskite solar cells

Abstract TiO 2 compact layers are wildly used for electron selective contact in perovskite solar cells. The function of TiO 2 selective contact can be modified by doping metal ions in the TiO 2 compact layers. As lanthanide elements usually exhibit unique properties for their incompletely occupied 5d or 4f orbitals, we prepared lanthanum doped TiO 2 compact layers by spray pyrolysis method as the electron selective contact of perovskite solar cells. SEM images indicate lanthanum dopants improve the smoothness of TiO 2 layers. In the optimized concentration, the average PCE of devices is promoted from 12.4% to 14.4% with the highest PCE of 17.2%, which comes from the improvement on charge transfer and recombination. Moreover, the Lanthanum dopants also lead to the improvement in photo-stability of perovskite solar cells. For the device with optimized La concentration, 80% of its original PCE is preserved after 200 h aging under continuous one sun illumination.