Hydrophobic hole-transporting layer induced porous PbI2 film for stable and efficient perovskite solar cells in 50% humidity

Stable and efficient planar perovskite solar cells have been demonstrated in a high relative humidity of 50% with a lead phthalocyanine (PbPc) hole-transporting layer (HTL). Porous PbI2 film is prepared on the PbPc HTL due to it hydrophobic property, which leads to a fast formation of a compact and homogeneous perovskite film with large grains. As a result, a power conversion efficiency (PCE) of 10.79% is obtained, which is comparable to the reference device with a traditional poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) HTL and one of the highest values among the reported perovskite solar cells prepared in a high humidity condition. More importantly, the device retains 45% of its maximum PCE after it is stored in high humidity condition in dark for 56 days, comparing to an almost full failure of the reference device after only 6 days. This improvement is attributed to the restricted absorption of moisture during device fabrication and storage processes.