All-inorganic metal oxide transparent solar cells

Different from the opaque conventional types, transparent solar cells (TSCs) have the great advantage of generating energy without blocking of human vision. And thus, this invisible power generator can be applied to cell phone screens, displays and windows of vehicles and buildings. The electric power conversion from UV absorption spontaneously removes the UV-induced damage on skin and eyes. All transparent solar cells were achieved by solid-state method. This dry-process ensures the long-term working device stability without any complex packaging processes of wet-type solar cells. Large-scale available sputtering was applied to deposit inorganic metal oxide layers. The sequential formation of p-NiO/n-TiO2 spontaneously forms the heterojunction and simultaneously drives the transparent photovoltaic cell. Apparently, the extension of light utilization of transparent solar cells is highly desirable to improve the performances, without scarifying transmittance at the same time. In order to tune TiO2 light response, the self-doped Ti3+ chemical state is formed which supports the transition of electrons, photo-generated by longer wavelength lights. The NiO/TiO2 TSC produces the highest photovoltage of 600 mV for UV light and also utilizes the longest wavelength of 740 nm. The TSC produced the photovoltage of 153.9 mV and photocurrent of 0.4 mA under the natural Sun light and can move a fan (0.3V and 2.5 mA) under LED light. The TSC would be an invisible power generator by supplying energy for human-electronics.