High-efficiency CuInxGa1−xSe2 solar cells made from (Inx,Ga1−x)2Se3 precursor films

Abstract

In, Ga, and Se were coevaporated to form precursor films of (Inx,Ga1−x)2Se3. The precursors were then converted to CuInxGa1−xSe2 by exposure to a flux of Cu and Se. The final films were smooth, with tightly packed grains, and had a graded Ga content as a function of film depth. Photovoltaic devices made from these films showed good tolerance in device efficiency to variations in film composition. A device made from these films resulted in the highest total-area efficiency measured for any non-single-crystal, thin-film solar cell, at 15.9%.

Development of thin‐film Cu(In,Ga)Se2 and CdTe solar cells

“…CIGS films prepared by the three-stage process exhibit a smooth surface, which reduces the junction area and thereby is expected to reduce the number of defects at the junction. 66 This smoother surface facilitates the uniform conformal deposition of a thin buffer layer and prevents ion damage in CIGS during sputter deposition of ZnO/ZnO:Al.…”

“…[61][62][63] An 'inverse' two-stage process starts with a precursor layer that is more Cu-poor than the finished film. 64,65 The so-called three-stage process, introduced by NREL, 66 is obtained by starting the deposition with an (In,Ga) x Se y precursor, followed by the co-deposition of Cu and Se until Cu-rich overall composition is reached, and finally the overall Cu concentration is readjusted by subsequent deposition of In, Ga and Se. 66 This method leads, up to now, to the most efficient solar cells.…”

“…64,65 The so-called three-stage process, introduced by NREL, 66 is obtained by starting the deposition with an (In,Ga) x Se y precursor, followed by the co-deposition of Cu and Se until Cu-rich overall composition is reached, and finally the overall Cu concentration is readjusted by subsequent deposition of In, Ga and Se. 66 This method leads, up to now, to the most efficient solar cells. CIGS films prepared by the three-stage process exhibit a smooth surface, which reduces the junction area and thereby is expected to reduce the number of defects at the junction.…”

Chemical incorporation of copper into indium selenide thin‐films for processing of CuInSe2 solar cells

“…The highest efficiency cells reported to date (19.5%) were made from copper-poor Cu(In, Ga)Se 2 (CIGS) deposited by the threestage process [1]. In this vacuum co-evaporation process an (In, Ga) 2 Se 3 layer is deposited and then converted into a Cu-rich CIGS layer by exposure to Cu and Se fluxes at high temperature before further evaporation of In, Ga and Se turn the layer Cu-poor [2]. A simpler approach might be advantageous for large-scale production of CIGS solar cells and so methods have been investigated that terminate the second stage before the CIGS layer composition turns Cu-rich [3][4][5][6].…”

Junction formation in CuInSe[sub 2]-based thin-film devices

“…The CIGS thin films used in this study were grown by the three-stage process described elsewhere (10). The experimental details for the deposition of CdS and ZnO layers can be found in ref (11,12).…”