Previously, open circuit voltage (Voc) of 960mV was reported on Se-free Cu(In,Ga)S2 solar cell with CdS buffer layer. In this paper, we report our latest progress toward 1000mV Voc on Se-free Cu(In,Ga)S2 solar cell with Cd-free buffer layer. Our highest Voc cell demonstrated Voc of 973mV thanks to rapid thermal annealing and Zn1-xMgxO buffer layer application.