Unraveling the relationship between the phenethylammonium-induced 2D phase on the perovskite surface and inverted wide bandgap perovskite solar cell performance

Abstract

Two- and three-dimensional (2D/3D) heterojunctions have been widely used to improve the performance of n-type/intrinsic/p-type (NIP) structured perovskite solar cells (PSCs). However, the electron blocking nature of the 2D ligands, such as phenethylammonium (PEA⁺), on the perovskite surface is not conducive to PSCs with a p-type/intrinsic/n-type (PIN) structure. In this work, we improve the device performance by eliminating the 2D phase on the perovskite surface through the subsequent annealing process. After eliminating the 2D phase, a dipole layer forms with the remaining PEA⁺, resulting in an excellent energy level alignment between the perovskite and electron transport layer. As a result, the solar cells with the PIN structure using a 1.67 eV wide-bandgap triple-cation perovskite show an enhanced power conversion efficiency of 20.61% with a short circuit current density of 20.05 mA cm⁻² and a fill factor of 81.57%. Furthermore, the open-circuit voltage (V_OC) is improved from 1.20 V to 1.26 V, yielding a V_OC deficit of 410 mV, which represents one of the lowest values among the PIN structured wide-bandgap PSCs.