Conventional CIGS absorber layers are formed by sputtering/selenization or co-evaporation technique. Since such a vacuum deposition requires high CAPEX, several companies and research institutes are developing cost effective non-vacuum technology. However, in non-vacuum technology, relatively low photoelectric conversion efficiency and its reproducibility are hurdles for commercialization.The non-vacuum technology consists of (1) CIGS precursor synthesis (2) CIGS precursor film coating using printing equipment such as a slot die, doctor blade, or spin coater, and (3) high quality CIGSSe absorber film formation by post-annealing such as selenization/sulfurization. Although appropriate coating method selection and coating/drying process optimization are the important factors for a dense and uniform precursor film, obtaining uniform CIGS absorber layer after selenization/sulfurization process is also critical for high efficiency and low deviation of run-to-run efficiency in CIGS photovoltaic cell.In this study, a significant carbon residue was found in CIGS absorber layer after those processes. It is believed that the carbon residue originated from the organic chemicals included in nanoparticle ink such as dispersant. It is inferred that the carbon residue prevents recrystallization of CIGS nano-particles and eventually reduces cell efficiency due to high recombination rate and series resistance. In order to control the carbon residue, low temperature pre-annealing process was carried out before high temperature selenization step. Six Sigma method was used to find the optimized condition of pre-annealing with a minimum number of experiments.

Carbon residue control in CIGS absorber layer formed by using CIGS nanoparticles

248th National Meeting (2014)

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