Water-based inks for inkjet-printed Cu(In, Ga)(S, Se)2 thin film solar cells with a power conversion efficiency of 15%

Abstract

As a highly promising on-demand manufacturing technology, inkjet printing offers a viable pathway for the cost-effective and large-scale production of thin-film solar cells. However, inkjet-printed Cu(In, Ga)(S, Se)₂ (CIGSSe) thin film solar cells typically exhibit lower power conversion efficiencies (PCEs) than their spin-coated counterparts. Moreover, the PCEs of CIGSSe solar cells fabricated using eco-friendly water-based precursor solutions have remained stagnant for many years. To address these challenges, this work introduces a novel water-based Cu(In, Ga)S₂ (CIGS) precursor ink with a tailored water/ethanol ratio, enabling the room-temperature and air-processed deposition of uniform and continuous CIGSSe films via inkjet printing. The optimized ink demonstrates excellent air stability, suitable viscosity, and favorable wettability, as systematically investigated through varying water/ethanol ratios. By optimizing the ink formulation, we achieved an encouraging PCE of 15.0% for water-based CIGSSe solar cells. Furthermore, this approach significantly enhances raw material utilization, thereby reducing material costs while maintaining environmental sustainability. Our findings pave the way for scalable and high-performance CIGSSe photovoltaics using an eco-friendly inkjet printing process.