Deposition of In2S3 on Cu(In,Ga)(S,Se)2 thin film solar cell absorbers by spray ion layer gas reaction: Evidence of strong interfacial diffusion

Abstract

Recently, Cd-free Cu͑In, Ga͒͑S,Se͒ 2 -based "CIGSSe" thin film solar cells with a nominal In 2 S 3 buffer layer deposited by the spray ion layer gas reaction technique resulted in photovoltaic performances comparable to that of CdS buffered references. In the past it was argued that diffusion processes across the In 2 S 3 / CIGSSe interface play a significant role for the device quality. Investigating the interface formation by using x-ray photoelectron spectroscopy, the authors were able to confirm a strong interfacial diffusion involving Cu and Na from the CIGSSe.

Nondestructive depth-resolved spectroscopic investigation of the heavily intermixed In2S3/Cu(In,Ga)Se2 interface

“…4,8,9 At ͑post-͒deposition annealing temperatures necessary for high device efficiencies ͑200-250°C͒, a pronounced diffusion of Cu and Na from the CIGSe/Mo/glass substrate into the nominal In 2 S 3 buffer layer was found in these studies. However, a complete picture of the chemical interface structure is still missing.…”

“…5 The In 2 S 3 /CIGSe interface has been previously investigated by different destructive depth-profiling techniques, 2,6 high-resolution transmission electron microscopy and energy dispersive x-ray analysis, 7 and x-ray photoelectron spectroscopy ͑XPS͒. 4,8,9 At ͑post-͒deposition annealing temperatures necessary for high device efficiencies ͑200-250°C͒, a pronounced diffusion of Cu and Na from the CIGSe/Mo/glass substrate into the nominal In 2 S 3 buffer layer was found in these studies. However, a complete picture of the chemical interface structure is still missing.…”

The spray-ILGAR® (ion layer gas reaction) method for the deposition of thin semiconductor layers: Process and applications for thin film solar cells

“…These results attest that the ILGAR buffer process is highly robust. lead to a Cu diffusion from the absorber to the buffer as shown by XPS [27] excluding the need for a post annealing step which is necessary for In 2 S 3 buffers deposited by ''cold substrate'' methods, such as physical vapour deposition [28]. The reason of the benefit of the copper migration into the buffer, e.g.…”

Role of Cl on Diffusion of Cu in In2S3 Layers Prepared by Ion Layer Gas Reaction Method

“…In2S3 has found increased attention in photovoltaic's as a replacement for toxic CdS [1][2][3][4] because of its suitable properties. It has been effectively used as a buffer layer for both chalcopyrite [1][2][3] and nanocomposites [5,6] solar cells and as an extremely thin absorber (eta) in eta cells [7,8] and nanocomposites [9] solar cells with ZnO nanorods or nanoporous-TiO2 electrodes, respectively.…”

“…It has been effectively used as a buffer layer for both chalcopyrite [1][2][3] and nanocomposites [5,6] solar cells and as an extremely thin absorber (eta) in eta cells [7,8] and nanocomposites [9] solar cells with ZnO nanorods or nanoporous-TiO2 electrodes, respectively. Diffusion of Cu from Cu(In,Ga)(S,Se)2 absorber [3,10,11] or CuSCN hole conductor [12] into In2S3 layers has been a major drawback to effective performance and stability of these solar cells.…”