Solution-based synthesis of dense, large grained CuIn(S, Se)2 thin films using elemental precursor

Abstract

Compared with the expensive and complicated vacuum techniques, the solution-based process to deposit I-III-VI2 chalcogenide thin films (I=Cu, III=In or Ga, VI=S or Se) has attracted great interests due to its lower cost, higher scalable production and better application in flexible substrate. Herein, a low-toxic and high-active mixture solvent comprised of 1, 2-ethanedithiol and 1,2-ethylenediamine is utilized to dissolve elemental Cu, In and S powders at 60°C, forming the CuInS2 (CIS) precursor solution. After spin coating and annealing in a both Ar gas and selenium atmosphere, a dense and large-grained chalcopyrite CuIn(S,Se)2 (CISSe) thin films with a close-packed grain size of ~800nm are prepared, eliminating a undesired fine fine-grained bottom layer. In addition, the selenization temperature of the CISSe thin films is also discussed, which influences the phase composition, crystallinity and morphology of CISSe thin films. Photovoltaic device of the CISSe-based thin films is fabricated, obtaining a power conversion efficiency of 6.2% with an active cell area of 0.5cm2 under AM 1.5 illumination.