Preparation of homogeneous Cu(InGa)Se2 films by selenization of metal precursors in H2Se atmosphere

Abstract

Homogeneous single phase Cu(InGa)Se2 films with Ga/(In+Ga)=0.25–0.75 were formed by reacting Cu–Ga–In precursor films in H2Se followed by an anneal in Ar. X-ray diffraction and Auger analysis show that the metal precursors reacted only in H2Se were multiphase films having a layered CuInSe2/CuGaSe2 structure. Solar cells made with the multiphase films have properties similar to CuInSe2 devices. Cells made with the annealed single phase films behave like Cu(InGa)Se2 devices with the band gap expected for the precursor composition.

Cu(In,Ga)Se<inf>2</inf> film formation from selenization of mixed metal/metal-selenide precursors

“…However, it is widely observed that Ga migrates away from the junction to the Mo back contact [2,3,4]. This backcontact Ga accumulation prevents the increase in bandgap near the junction that is needed for the achievement of high voltage solar cells.…”

“…Furthermore, the decomposition of Cu9Ga4 intermetallic remaining at the backside of the film is the rate-limiting step in the selenization process. Although Ga homogenization can be achieved with an additional annealing process [2] or a two-stage growth technique [5], reaction processes that directly yield uniform Ga distribution through the CIGS films are desired.…”

Use of diethylselenide for the preparation of CuInGaSe 2 films by selenization of metal precursors premixed with Se

“…These results are remarkably different from those reported for the selenization of Cu-In-Ga precursors using H 2 Se or elemental Se, as follows. When H 2 Se or elemental Se was used, In tended to diffuse toward the surface and Ga toward the substrate, giving rise to phase separation into CIS and CGS [3][4][5]11]. In this case, CIGS alloy was not formed although a variety of Se sources and stacking structures were attempted [3][4][5]11].…”

The second‐generation of CdTe and CuInGaSe2 thin film PV modules

“…CuIn 1-x Ga x Se 2 /CdS (with x=0.25) thin film solar cells can exhibit an efficiency around 20% [4][5][6][7][8]. This is the highest efficiency ever obtained for a thin film solar cell and it is comparable with the best crystalline Si solar cells.…”