Tuning of Precursor Composition and Formation Pathway of Kesterite Absorbers Using an In‐Process Composition Shift: A Path toward Higher Efficiencies?

This work reports a growth process for tuning the formation pathway and final composition of kesterite Cu2ZnSnSe4 (CZTSe) thin film absorbers. By adjusting as-grown precursor, can be started in Cu-rich, stoichiometric, or Cu-poor environment. During high-temperature stage annealing process, incorporation loss SnSe2–x vapor at layer is used to achieve an in-process shift during further (e.g., Cu-rich Cu-poor/Cu-poor toward Cu-rich). approach partially decouples precursor absorber, which, thus, tuned independently. The growth, specifically tracked by interruption experiments. influence starting resulting absorber on optoelectronic properties device performance solar cells discussed. results show refined region reduced Urbach tailing lower V OC deficit. best efficiencies > 11% deficit < 320 mV (relative Shockley–Queisser limit).