Sunlight-activated graphene-heterostructure transparent cathodes: enabling high-performance n-graphene/p-Si Schottky junction photovoltaicsElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ee00548e

Compared to widely-reported graphene-based anodes, the task of obtaining a stable graphene-based cathode is generally more difficult to achieve because n-type graphene devices have very limited thermal and chemical stabilities, and are usually sensitive to the influence of the ambient environment. This work developed a novel "sunlight-activated" graphene-heterostructure transparent electrode in which photogenerated charges from a light-absorbing material are transferred to graphene, resulting in the modulation of electrical properties of the graphene transparent electrode caused by a strong light-matter interaction at graphene-heterostructure interfaces. A photoactive graphene/TiO x -heterostructure transparent cathode was used to fabricate an n-graphene/p-Si Schottky junction solar cell, achieving a record-high power conversion efficiency (>10%). The photoactive graphene-heterostructure transparent electrode, which exhibits excellent tunable electrical properties under sunlight illumination, has great potential for use in the future development of graphene-based photovoltaics and optoelectronics. A record-high efficiency (>10%) was achieved for an n-graphene/p-Si Schottky junction solar cell by using the "sunlight-activated" graphene/TiO x transparent cathode.