Giant V _oc Boost of Low‐Temperature Annealed Cu(In,Ga)Se ₂ with Sputtered Zn(O,S) Buffers

An open circuit voltage boost from 0.33 to 0.50 V is reported by M. Zutter et al. (article no. 1900145) for solar cells comprising industrial-grade Cu(In,Ga)Se2 absorbers and sputtered Zn(O,S) buffer layers. The research shows that thermal annealing up to 200 °C shifts the dominant recombination pathway from interface to bulk. Concurrently, ultraviolet-photoelectron spectroscopy reveals an increase of the work function of Zn(O,S) films deposited on Cu(In,Ga)Se2. The change of conduction band offset and the observed wavelength-dependent improvement of charge-carrier collection are consistent with solar cell capacitance simulations. The study identifies future steps needed to achieve efficient cells based on all-vacuum processed components.