Simultaneous bulk defect passivation and enhanced electron extraction in inverted perovskite solar cells via nonfullerene Y6 anti-solvent assisted gradient heterostructure

Trap state inducing nonradiative recombination is a main obstacle for achieving high-efficiency metal-halide perovskite photovoltaics. Here, we introduced a straightforward strategy by utilizing a functional additive in perovskite antisolvent to ameliorate the quality of perovskite film. The additive Y6, extensively applied in organic optoelectronics as electron donor, possesses capacity to coordinate with the lead ion (Pb2+) through the formation of Lewis adducts. The introduction of nonfullerene Y6 effectively suppressed nonradiative recombination through passivating the electronic defects, such as undercoordinated Pb2+ or Pb clusters, abating defects density to acquire high quality films with improved stability, simultaneously enabling a well-matched energy alignment at interface between perovskite/electronic transport material to elevate charge extraction through graded heterojunction structure, ultimately providing planar inverted perovskite solar cells with power conversion efficiency up to 20.6% from current-voltage measurements and a steady-state 20.3% power output. This work demonstrates Y6-based antisolvent engineering delivers a multifunctional promising method permitting perovskite films with enlarged grain sizes and diminished defects density by forming Lewis adducts intermediate, simultaneously obtaining interfacial gradient heterostructure to facilitate charge transfer processes.