Fabrication and characterization of titanium dioxide (TiO2)/selenium thin‐film solar cells

Abstract

AbstractRecently, Se‐based low‐cost thin‐film solar cells have been developed, resulting in an improvement of the conversion efficiency over conventional Se photocells. Although these solar cells enable increasing the photocurrent increase by designing a thin Se layer, no considerations have been given for the open‐circuit voltage.The TiO2/Se solar cell described in this paper uses n‐type TiO2 with remarkable photoconductivity as a window material. In addition, it reduces the dark current and improves the open‐circuit voltage by operating as an MIS (Metal‐Insulator‐Semiconductor) diode in the dark and as a pn junction under the light illumination. As a result, the open‐circuit voltage has been improved, and a cell with a conversion efficiency of 5.0 percent (short‐circuit current is 10.8 mA/cm2, open‐circuit voltage 0.88 V, fill factor FF 0.53) under simulated AM 1.5 (100 mW/cm2) illumination has been realized. This is the highest efficiency reported to date for Se solar cells.Additionally, since the spectral response is close to the emission spectrum of fluorescent lights, the efficiency improves to 11 ‐ 13 percent under fluorescent lights (500 lux). Furthermore, since these cells have advantages of high sensitivity in short wavelengths, good photocurrent‐illumination characteristics and low dark current, applications not only for solar cells but for light sensors such as color sensors and power meters are also expected.