Suppressed Formation of Conductive Phases in One-Pot Electrodeposited CuInSe2 by Tuning Se Concentration in Aqueous Electrolyte

Abstract

The single-bath electrochemical deposition of CuInSe2 often leads to short-circuit behavior of the resulting solar cells due to,lhe high shunt conductance. In this, study, in amattemp't to resolve this problem, the influence of the Se precursor concentration (C-se) on electrodqpOsited CuInSe2 films and solar cell devices is examined in the C-Se range of 4.8 to 12:0 mM in selenite-based aqueous solutions ':containing Cu and In chlorides along with sulfarnic acid (H3NSO3) and potassium hydrogen phthalate (C8H5KO4) additives. As C-se increases,, the CuInSe2 layers become porous; and the grain, growth of the CuInSe2 phase is restricted,-while the parasitic shunting problem wag-markedly alleviated, as unambiguously demonstrated by measurements of the local current distribution. Due to these ambivalent influences, an optimal value of cse that achieves the best quality of the films for high-efficiency solar cells is identified. Thus, the.device prepared with 5.2 mM C-Se exhibits a power-conversion efficiency exceeding 10% with greatly improved device parameters, such as the shunt conductance and the reverse saturation current. The rationale of the present approach along-with the physicochemical,origin of its conspicuous impact on the resulting devices is discusSed in-conjunction with the electro-crystallization mechanism-of the CuInSe2 compound.