Practical Interface Engineering between Perovskite and Carbon Electrode in Regular Carbon-Based Perovskite Solar Cells

Despite the continuous growth in power conversion efficiencies (PCEs) of hole transport layer-free carbon-based perovskite solar cells (HTL-free C-PSCs) due to their enhanced stability and low-cost structure, their performance still lags behind the Shockley-Queisser limit (∼33%) for CH₃NH₃PbI₃ PSCs and even regular PSCs with HTL and metal counter electrodes (26.9%). This discrepancy primarily stems from poor physical contact at the perovskite/carbon interface, energy band alignment mismatch, and the inability of the carbon electrode (CE) to reflect incident light. To address these issues, specialized methods and strategies have been developed, yet a comprehensive review focusing on interface engineering between perovskites and CEs in regular C-PSCs remains lacking. This Review highlights recent research progress in interface engineering for C-PSCs, with particular emphasis on modifications at the perovskite/CE interface. It also provides a brief outlook on the challenges and opportunities in advancing the efficiency and stability of C-PSCs through a tailored interfacial engineering. A comprehensive overview diagram is presented that summarizes the unique properties of carbon, the key challenges faced by C-PSCs, and the interfacial engineering strategies employed.