Beyond Conventional Designs: Dual Gradient Strategies Unlock 22.5% PCE in Carbon‐PSCs

Abstract

All‐inorganic perovskite solar cells with carbon electrodes (C‐IPSCs), which bypass the need for a hole‐transport layer (HTL), have attracted considerable interest because of their exceptional stability and low production costs. Nevertheless, their power conversion efficiencies (PCEs) remain lower compared to HTL‐integrated hybrid perovskite solar cells (HPSCs). To bridge this performance gap, this work proposes an innovative C‐IPSC architecture incorporating gradient doping profiles and a graded electron affinity within the absorber layer. The design employs CsPbI 3 as the photoactive material and is rigorously analyzed through numerical simulations using SCAPS‐1D. Key parameters, including CsPbI 3 thickness, gradient doping distributions, average doping concentrations, and electron affinity gradients, were systematically optimized to enhance device performance. Comprehensive investigations of the energy band configuration, charge carrier recombination mechanisms, and built‐in electric field ( E bi ) dynamics revealed that gradient doping induces a tailored E bi . This field facilitates directional charge transport across interfacial layers, significantly improving carrier extraction and reducing recombination losses. Furthermore, to address energy‐level misalignment at material interfaces, an electron affinity gradient strategy was implemented. This approach optimizes energy‐level alignment, creating continuous charge transport pathways while suppressing interfacial recombination. The synergistic integration of gradient doping and electron affinity engineering resulted in a marked enhancement of photovoltaic efficiency for C‐IPSCs. These findings underscore the potential of gradient‐based structural modifications in advancing C‐IPSCs as durable, high‐performance, and economically viable alternatives to conventional HTL‐dependent architectures. The proposed design principles offer a promising pathway toward overcoming efficiency limitations in all‐inorganic perovskite photovoltaics.