Low‐Temperature Growth of Submicron Cu(In, Ga)Se₂ Solar Cells Based on Molybdenum Oxide Back Interface Layer

Abstract

Cu(In,Ga)Se 2 (CIGS) thin film solar cells are proven to be highly efficiency. However, lowering the substrate temperature and reducing absorber layer thickness can lead to severe light and electric losses. In this work, the authors employ molybdenum oxide acting as back interface layer in order to decrease the recombination at the rear interface in low-temperature growth of submicron CIGS solar cells. X-ray photoelectron spectroscopy (XPS) results show that the compositions of molybdenum oxide films are mainly MoO x (2 < x < 3) under the influence of metal molybdenum substrate and CIGS absorber. Meanwhile, the authors study the properties of CIGS devices with different MoO x thicknesses. They find that MoO x with appropriate thickness can facilitate the crystallization of CIGS absorber layer and restrain the recombination in the CIGS bulk as well as at the back interface. Finally a CIGS solar cell with active area efficiency of 11.8% is fabricated by lowtemperature processes below 450 C when the thicknesses of absorber layer and molybdenum oxide are 0.92 and 10 nm, respectively. Compared with the reference device, absolute increase about 40 mV and 13% for V oc and FF are achieved.

A Comprehensive Perspective on the Fabrication of CuGaSe2/Si Tandem Solar Cells

“…Thermal evaporation is also helpful for MoO 3 deposition for CIGS solar cells. [ 130 ] Similar to MoO 3 , thermally evaporated WO 3 works as the interlayer. The thin oxide interlayer between ITO and CIGS facilitates tunnel transport of holes to back contact.…”