Journal Article solar cells 46F059V66A 789U1901C5 Buffers CH46OC8YV4 CZTSSe Copper Gallium Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. T8BEA5064F charge transport congruent evaporation crystallite size cuprous oxide doping concentration double emitter earth-abundance electro-optical materials gallium oxide indium sulfide ligand exchange perovskite quantum dots  photovoltaic devices re-assembling process short-circuit current density thin films thin-film solar cells tin sulfide