Two Anthracene-Based Copolymers as the Hole-Transporting Materials for High-Performance Inverted (p-i-n) Perovskite Solar Cells

Two anthracene-based copolymers, the thiophene-bridged carbazole-anthracene copolymer (abbreviated as PCBZANT) and the thiophene-bridged triphenylamine-anthracene copolymer (abbreviated as PTPAANT), have been developed as the hole-transporting materials (HTMs) for the inverted perovskite solar cells. They were thermally stable with decomposition temperatures of 435 and 420 °C. The High Occupied Molecular Orbitals (HOMO) of -5.15 and -5.24 eV of two copolymers facilitated the hole carriers transfer from the perovskite layer (CH₃NH₃PbI₃, HOMO: -5.4 eV) in contrast to poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS, HOMO: -4.9 eV). The solar cell with PCBZANT (abbreviated as the PCBZANT device) showed the highest power conversion efficiency (PCE) of 15.50%, while the cell with PTPAANT (abbreviated as the PTPAANT device) showed the highest PCE of 14.52%, with increases of 36.2% and 27.6%, respectively, relative to the PEDOT:PSS device. The thorough analysis disclosed that the high performance was mainly ascribed to the enhanced open-circuit voltage (V_OC) and short-circuit current density (J_SC), being contributed from the efficient hole-carrier extraction, the high hole mobility of two copolymers, and the high-quality perovskite film with large crystal size and less defect. With strong absorption in the range of 350-500 nm, the polymers decreased the destruction of UV-radiation on the perovskite layer as UV-filters and improved the stability of the inverted cells.