Dopant-free 3,3′-bithiophene derivatives as hole transport materials for perovskite solar cells

Three 3,3'-bithiophene derivatives (DHPT-SC, DOPT-SC and DEPT-SC) have been efficiently synthesized by a Stille reaction. X-ray diffraction analysis revealed unique swivel-cruciform configurations and weak intermolecular pi-pi stacking in these materials. Perovskite solar cells using these pristine hole transport materials without dopants have achieved power conversion efficiencies of 8.35%, 8.69%, and 9.73% with good air stability. This present finding develops dopant-free hole transport materials for perovskite solar cells.