Transparent photovoltaic cells and self-powered photodetectors by TiO2/NiO heterojunction

The transparent photovoltaic cell (TPC) is an invisible solar cell by passing the visible range light while absorbing harmful UV light to generate electric power. Different from the conventional opaque colors or shapes of solar cells, TPC is transparent to human eyes and which would serve as an invisible power source for the window frames of mobile electronics, displays, and buildings. To fabricate the TPC, two different metal-oxide species are employed to make a transparent heterojunction. TiO2 is the n-type semiconductor and serves as the UV light absorber. Above TiO2 layer, p-type NiO is deposited for a high transmittance (>57%) for the visible light. The TPC is very sensitive to UV signals and thus, TPC can be a high-performing photodetector by self-powered operation due to the photovoltaic effect. The n-TiO2/p-NiO photodetector shows high responsivity (0.23 A W-1), detectivity (1.6 x 10(10)), and fast response time (4.1 ms). The power conversion efficiency of TPC is reached to 2.1% with high open circuit voltage (>0.5 V). A practical demonstration is performed to move a motor (0.2 V and 10 mA), powered by TPC. This clearly suggests the transparent solar cell as the invisible power generator.