A 2D/3D Heterostructure Perovskite Solar Cell with a Phase‐Pure and Pristine 2D Layer

Abstract

Interface engineering plays a critical role in advancing the performance ofperovskite solar cells. As such, 2D/3D perovskite heterostructures are ofparticular interest due to their optoelectrical properties and their furtherpotential improvements. However, for conventional solution-processed 2Dperovskites grown on an underlying 3D perovskite, the reaction stoichiometryis normally unbalanced with excess precursors. Moreover, the formed 2Dperovskite is impure, leading to unfavorable energy band alignment at theinterface. Here a simple method is presented that solves both issuessimultaneously. The 2D formation reaction is taken first to completion, fullyconsuming excess PbI2 . Then, isopropanol is utilized to remove excessorganic ligands, control the 2D perovskite thickness, and obtain a phase-pure,n = 2, 2D perovskite. The outcome is a pristine (without residual 2Dprecursors) and phase-pure 2D perovskite heterostructure with improvedsurface passivation and charge carrier extraction compared to theconventional solution process. PSCs incorporating this treatmentdemonstrate a notable improvement in both stability and power conversionefficiency, with negligible hysteresis, compared to the conventionalprocess.