Poly(9-vinylcarbazole) as a hole transport material for efficient and stable inverted planar heterojunction perovskite solar cells

Conjugated polymer poly(9-vinylcarbazole) (PVK) has been explored as an efficient hole transport material (HTM) to replace poly(3,4-ethylenedio-xythiophene): poly(styrenesulfonate) (PEDOT:PSS) for the preparation of p-i-n type, inverted planar heterojunction perovskite solar cells. The PVK film can be facilely deposited by room-temperature solution-casting without any doping or post treatments. Using MAPbI 3 as the photoactive layer, a 15.8% stabilized power conversion efficiency was achieved in ITO/PVK/MAPbI 3 /PCBM/Ag devices, which is a significant improvement compared with 12.1% from devices using PEDOT:PSS as the HTM. The perovskite photoactive layer cast on PVK HTM has higher crystallinity and less PbI 2 residues, leading to a higher charge recombination resistance of the device. After a storage of 1000   h, the PCE of PVK- and PEDOT:PSS- based devices dropped to 82.5% and 56% respectively, and demonstrated that the PVK-based perovskite devices is more stable compared with the PEDOT:PSS-based devices.