19.2% efficient InP heterojunction solar cell with electron selective TiO2 contact

Abstract

We demonstrate an InP heterojunction solar cell employing an ultrathin layer (similar to 10 nm) of amorphous TiO2 deposited at 120 degrees C by atomic layer deposition as the transparent electron-selective contact. The TiO2 film selectively extracts minority electrons from the conduction band of p-type InP while blocking the majority holes due to the large valence band offset, enabling a high maximum open-circuit voltage of 785 mV. A hydrogen plasma treatment of the InP surface drastically improves the long-wavelength response of the device, resulting in a high short-circuit current density of 303 mA/cm(2) and a high power conversion efficiency of 19.2%.