Greatly enhanced power conversion efficiency of hole-transport-layer-free perovskite solar cell via coherent interfaces of perovskite and carbon layers

The interfacial contact between a perovskite and a carbon layer significantly affects the photovoltaic performance of a paintable and carbon-based hole transport material (HTM)-free perovskite solar cell (PSC). However, the detailed mechanism of the performance degradation, with regard to the carrier dynamics behavior at the perovskite/carbon interface, has not been elucidated yet. In this study, the improved interface of the perovskite/carbon was designed via a newly carbon electrode with nanosized carbon black and carbon fibers. Meanwhile, the modified Mott-Schottky analysis is conducted to study the carrier dynamics in the coherent and sparsely contacting interfaces, revealing that the unrestricted excitons in the nanoscale non-contact region of the coherent interface can be separated and then drove to be transported by the lateral built-in electric field. Furthermore, the HTM-free PSC via improved material design and fabrication by using a bilayer carbon electrode (coherent layer and conductive layer) results in an enhanced champion efficiency of 14.1%.