Enhancing the performance of planar heterojunction perovskite solar cells using stable semiquinone and amine radical modified hole transport layer

Highly efficient organic-inorganic hybrid planar heterojunction perovskite solar cells with an architecture of indium tin oxide (ITO)/PEDOT:PSS-NH2-OH/CH3NH3PbI3/PCBM/Al are fabricated via one-step, solution process by employing the dopamine modified PEDOT:PSS (PEDOT:PSS-NH2-OH) as the hole transport layer, of which the power conversion efficiency of 15.34% is achieved with negligible hysteresis regardless of different scanning directions and scanning speeds. The average efficiency of twenty devices with PEDOT:PSS-NH2-OH is increased to 14.16% from 10.67% with PEDOT:PSS, and the former devices exhibit good reproducibility with small standard deviations. Cyclic voltammetry results show that the highest occupied molecular orbital energy level of PEDOT:PSS-NH2-OH (5.32 eV) matches well with the valence band of CH3NH3PbI3 absorbers (5.4 eV). Photoluminescence measurements indicate that the CH3NH3PbI3 film deposited on PEDOT:PSS-NH2-OH has strong charge extraction capability than that on PEDOT:PSS. Electrochemical impedance spectroscopy results suggest that the photovoltaic devices exhibit efficient hole transport and excellent electron blocking employing PEDOT:PSS-NH2-OH as the hole transport layer, as well as have low series, contact resistance and large recombination resistance. The research demonstrates that the stable semiquinone and amine radical modified PEDOT:PSS can acts as an outstanding hole transport material for fabricating high-efficient perovskite solar cells.