Guijarro, NestorPrevot, Mathieu S.Johnson, MelissaYu, XiaoyunBouree, Wiktor S.Jeanbourquin, Xavier A.Bornoz, PaulineLe Formal, FlorianSivula, Kevin2017-02-172017-02-172017-02-17201710.1088/1361-6463/aa524chttps://infoscience.epfl.ch/handle/20.500.14299/134503WOS:000391746900002The realization of photoelectrochemical tandem cells for efficient solar-to-hydrogen energy conversion is currently impeded by the lack of inexpensive, stable, and efficient photocathodes. The family of sulfide chalcopyrites (CuInxGa1-xS2) has recently demonstrated a remarkable stability and performance even when prepared by solution-based routes that potentially lower the cost of fabrication. However, the photovoltage delivered by the photocathodes is still well-below the attainable values, a classical limitation linked to a large density of surface states in these materials. In the present work, we show that the identity of halide present during the growth of the solution-processed CuIn0.3Ga0.7S2 (CIGS) thin-films governs the overall performance by directing the crystal growth and the passivation of surface states. Replacing chlorine by iodine leads to CIGS photocathodes that deliver photocurrents of 5 mA cm(-2) (at 0 V versus RHE) and a turn-on voltage of 0.5 V versus RHE without charge extracting overlayer nor any sign of deterioration during stability test.chalcopyriteCu(InGa)S-2water splittingphotoelectrochemistrysemiconductor nanocrystalstext::journal::journal article::research article