Microstructural investigation of inkjet printed Cu(In,Ga)Se2 thin film solar cell with improved efficiency

摘要： Inkjet printed copper indium gallium diselenide (CIGS) thin film solar cell has attracted tremendous attention because of its various technological benefits as a non-vacuum process. Focused efforts in selenization of inkjet printed films to make the process feasible, are desired. In this work, microstructural investigation of inkjet printed precursor film selenized by rapid thermal processing (RTP) is presented. The optimization of selenization time for transforming metal nitrates precursor ink to CIGS thin film is investigated. Based on the results, the growth mechanism to form CIGS from inkjet printed CIG precursor films is proposed. Systematic study on the molybdenum diselenide (MoSe2) phase evolution during the two-step atmospheric pressure selenization process at the CIGS-Mo interface and its effect on device performance are carried out. Non-uniform inter-diffusion of indium (In) and gallium (Ga) during selenization, resulting in double-layered CIGS, one of the major reason limiting the performance of the devices is investigated through XRD, Raman, FESEM, EDS and Mott-Schottky analysis. The significant improvement in device efficiency from 0.4% to 4.2% is achieved due to microstructural improvement in CIGS films. Investigation on the mechanism of microstructural growth with selenization time affecting final device performance is presenting in this work.