In donor:acceptor bulk heterojunction organic solar cells, the chemical miscibility between different components and phase evolution dynamics within thin films often induce phase segregation and molecular aggregation/ orientation, both of which are film-depth-dependent. This leads to strong variations of molecular energy levels, photon absorption, exciton generation, charge transfer, and transport along film-depth direction. However, currently there is a lack of comprehensive investigation of filmdepth-dependent optical and electronic variations on the photovoltaic performance. In this work, using the recently developed film-depthdependent light absorption spectroscopy which simultaneously reveals vertical optical and electronic variations, the performance of organic solar cells is correlated with film-depth-dependent profiles of photon absorption and charge transport energy levels, which is subsequently compared with experimentally observed open-circuit voltage, short-circuit current, and efficiency. Because both light interference and vertical material variations contribute to film-depth-dependent exciton generation profiles, the local gradient of transport energy levels which provides extra built-in electric force could accelerate the dissociation of excitons and transport of free charges to avoid recombination, leading to high photovoltaic performance. A new method is therefore proposed to improve the photovoltaic performance by simultaneously tuning the film-depth-dependent optical and electronic distributions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.