Transparent All-Oxide Photovoltaics and Invisible Photodetectors

Abstract

Could transparent solar cells work as the invisible power generator? Is it possible, in order to satisfy the on-site energy production, to install the transparent solar cell into the window of buildings and vehicles without recognizing the existence of energy harvesting entities? Here we propose and demonstrate the wide energy bandgap materials for visible light transmittance and UV photon absorption for power generation. All-transparent solar cell was achieved by the heterojunction of metal oxide layers. Heterostructure of wide-bandgap materials have great potential for use in transparent optoelectronics for examples ultraviolet photodetectors, transparent solar cells, and transparent electronics. This study demonstrates the exciton, band-to-band and intermediate-band optical transitions in a ZnO/NiO heterostructure at room temperature. This heterostructure exhibits Ohmic current voltage characteristics close to that of various metal contacts such as Ag, C, Ni, and Au. Temperature-dependence studies revealed that the open-circuit voltage (VOC) of ZnO/NiO heterostructure is limited by the charge-transfer potential, analogous to excitonic solar cells. A negligibly small dark current of 1.6 × 10−8 A, a large VOC of 675 mV and a photoresponse speeds of 9.4 μs make it promising for high-speed energy-efficient optoelectronics. The optoelectronic performances of the ZnO/NiO/Ag microink suggest that broadband photons can be utilized with incident photons to current conversion efficiencies (IPCEs) of 2% and 39% in the visible and ultraviolet regions, respectively which demonstrate that the ZnO/NiO heterostructure can acts as a broadband quantum optoelectronic device.