Fast chemical bath deposition process at room temperature of ZnS-based materials for buffer application in high-efficiency Cu(In,Ga)Se₂-based solar cells

Chemical bath deposited (CBD) Zn(S,O) remains one of the most studied Cd-free buffer layers for Cu(In,Ga)Se₂-based (CIGSe) solar cells and has already been implemented at the industrial level for high-efficiency solar cells and modules. Exploring further routes of improvement is demanded and needed. One of the key routes is related to the high reactant concentration and high deposition temperature used for CBD-Zn(S,O). In this paper, we present a new family of reactants, based on hydroxylamine, presenting a high nucleophilic power and reactivity toward thiourea. We will show that the addition of these reactants allows to divide the concentration of thiourea by 3 and to perform Zn(S,O) deposition at room temperature. Efficiencies similar or even higher than the classical CBD cadmium sulfide are obtained due to higher J_sc and FF of the CIGSe-based solar cells. Growth mechanism and impact of hydroxylamine on the composition of the Zn(S,O) and cell performances will be discussed.