High-efficiency solar cells based on Cu(InAl)Se2 thin films

Abstract

A Cu(InAl)Se2 solar cell with 16.9% efficiency is demonstrated using a Cu(InAl)Se2 thin film deposited by four-source elemental evaporation and a device structure of glass/Mo/Cu(InAl)Se2/CdS/ZnO/indium tin oxide/(Ni/Algrid)/MgF2. A key to high efficiency is improved adhesion between the Cu(InAl)Se2 and the Mo back contact layer, provided by a 5-nm-thick Ga interlayer, which enabled the Cu(InAl)Se2 to be deposited at a 530 °C substrate temperature. Film and device properties are compared to Cu(InGa)Se2 with the same band gap of 1.16 eV. The solar cells have similar behavior, with performance limited by recombination through trap states in the space charge region in the Cu(InAl)Se2 or Cu(InGa)Se2 layer.