Solution-processed sulfur depleted Cu(In, Ga)Se2 solar cells synthesized from a monoamine–dithiol solvent mixture

Abstract

Molecular precursor processing from homogeneous and stable precursor solutions has become an important thrust in inorganic thin-film research because of its potential to provide low-cost, robust, and high-throughput deposition of various semiconductor films and devices. Here we demonstrate a versatile monoamine–dithiol mixture which possesses the remarkable ability to rapidly dissolve a variety of metal salts and metal chalcogenides under ambient conditions for the fabrication of device quality Cu(In, Ga)Se₂ (CIGSe) films. By using soluble precursors, an ultrathin CIGSe film solar cell with an undetectable level of sulfur with an efficiency of 10.3% has been fabricated for a total cell area of 0.457 cm². We further report an optimization study of the film composition and grain growth for a thicker CIGSe absorber layer, which has led to an increased solar cell efficiency of 12.2%, the highest reported values for solar cells using an amine–thiol solvent system. This study outlines a simple strategy to formulate inorganic semiconductor inks for processing high-quality selenide absorber layers of multinary compounds, which shows promise for increasing the efficiency of solution-processed thin-film solar cells.