Fabrication of dense CIGS film by mixing two types of nanoparticles for solar cell application

Abstract

Solution method fabrication of copper indium gallium selenide (CIGS) solar cells has attracted researchers due to easy fabrication and cost effective potential. Despite the encouraging results, the process of fabrication of solution processed solar cell faces challenges like use of toxic chemicals, high temperature processing to achieve large grain and dense CIGS absorber film for highly efficient device. Even though many methods have been developed, the voids generated in the CIGS absorber film after high temperature processing adversely affect the performance of fabricated CIGS solar cell to reach its maximum efficiency up to 20% which has already been achieved for vacuum deposited CIGS absorber film. A dense CIGS absorber film can be deposited by tailoring the size of nanoparticles in the ink solution. In this work, two types of nanoparticles, one having 200–500 nm size nanopowder prepared by ball-milling and other with 20–30 nm nanoparticles prepared using chemical solution route are mixed to prepare ink solution and deposited on the substrate to achieve dense and voids free absorber CIGS film . The smaller CIGS nanoparticles were found to occupy voids generated among the bigger CIGS nanopowder under low temperature sintering process. The performance of fabricated solar cells was found to improve when the concentration of smaller nanoparticles increases in the mixture. Solar cell fabricated with CIGS absorber layer deposited using mixture of nanoparticles exhibited 2.1% efficiency whereas only bigger nanopowder absorber film hardly exhibited any photovoltaic response under sintering at 250°C in ambient atmosphere.