Bithiophene-based cost-effective hole transport materials for efficient n-i-p perovskite solar cells

Three cost-effective hole transport materials, namely TP-H, TP-OMe and TP-F, were designed and synthesized by introducing several advantages of planar bithiophene formed by large steric hindrance of bulky group, intramolecular non-covalent interaction and passivation effects from F and S atoms.PSCs with doped TP-F as hole transport layer achieved a power conversion efficiency of over 24%.