Photoresponse in graphene/n-Si heterojunction and related photovoltaic properties

Graphene films were obtained on copper substrates by chemical vapor deposition (CVD), graphene/n-Si heterojunctions were produced by transferring graphene films onto n-Si substrates, and the photoresponse and photovoltaic properties in graphene/n-Si heterojunction were investigated. The structure of graphene was characterized by Raman spectrum and high-resolution transmission electron microscopy (HRTEM). Graphene field effect transistor was also produced to investigate the electrical properties of graphene. Using photolithography and plasma etching process, the graphene/n-Si heterojunctions were prepared. The optical and electrical properties of the heterojunction were tested under standard light source. The results demonstrated that the as-grown graphene was single layer and showed p-type field effect with a field-effect mobility of 3900 cm2·V-1·s-1 at room temperature. The graphene/n-Si heterojunction showed good rectification characteristics and excellent photovoltaic properties. The open circuit voltage and short-circuit current were 0.28 V and 0.87 mA, respectively, and the filled factor was 0.37. The heterojunction also showed good response capability and stability. The rise time was 96.9 ms and the decay time was 84.9 ms. The current remained unchanged after multiple cycles, showing good stability and response capability. The mechanism of the heterojunction with good photoresponse and photovoltaic properties was analyzed and it was considered that high electron mobility and good optical transparency of graphene played key roles. ©, 2015, Editorial Office of Chinese Journal of Rare Metals. All right reserved.