We report the influence of carrier reflector and back surface field generated by doped graphene on n-ZnO nanoridges/p-silicon photodetectors and silicon solar cells. It is found that the p-type graphene not only acts as an electron blocking layer, but also helps the collection of photogenerated holes. Quite surprisingly, the on/off ratio of the photodetector with the insertion of doped graphene can be increased by up to 40 times. Moreover, we demonstrate that typical silicon solar cells with the doped graphene, the cell efficiency can be enhanced by about 20. Our approach would expand numerous applications for graphene-based optoelectronic devices.
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