CdS/CdTe Solar Cells Containing Directly-Deposited CdSxTe1-x Alloy Layers

Conference · Sat Jan 01 04:00:00 EST 2011

DOI:https://doi.org/10.1109/pvsc.2011.6185966· OSTI ID:1049624

Duenow, J N; Dhere, R G; Moutinho, H R; To, B; Pankow, J W; Kuciauskas, D; Gessert, T A

A CdS{sub x}Te{sub 1-x} layer forms by interdiffusion of CdS and CdTe during the fabrication of thin-film CdTe photovoltaic (PV) devices. The CdS{sub x}Te{sub 1-x} layer is thought to be important because it relieves strain at the CdS/CdTe interface that would otherwise exist due to the 10% lattice mismatch between these two materials. Our previous work [1] has indicated that the electrical junction is located in this interdiffused CdS{sub x}Te{sub 1-x} region. Further understanding, however, is essential to predict the role of this CdS{sub x}Te{sub 1-x} layer in the operation of CdS/CdTe devices. In this study, CdS{sub x}Te{sub 1-x} alloy films were deposited by radio-frequency (RF) magnetron sputtering and co-evaporation from CdTe and CdS sources. Both RF-magnetron-sputtered and co-evaporated CdS{sub x}Te{sub 1-x} films of lower S content (x<;0.3) have a cubic zincblende (ZB) structure akin to CdTe, whereas those of higher S content have a hexagonal wurtzite (WZ) structure like that of CdS. Films become less preferentially oriented as a result of a CdCl{sub 2} heat treatment (HT) at {approx}400 C for 5 min. Films sputtered in a 1% O{sub 2}/Ar ambient are amorphous as deposited, but show CdTe ZB, CdS WZ, and CdTe oxide phases after a CdCl{sub 2} HT. Films sputtered in O{sub 2} partial pressure have a much wider bandgap than expected. This may be explained by nanocrystalline size effects seen previously [2] for sputtered oxygenated CdS (CdS:O) films. Initial PV device results show that the introduction of a directly-deposited CdS{sub x}Te{sub 1-x} alloy layer into the device structure produces devices of comparable performance to those without the alloy layer when a CdCl{sub 2} HT is performed. Further investigation is required to determine whether the CdCl{sub 2} heat treatment step can be altered or eliminated through direct deposition of the alloy layer.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO.
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy Solar Energy Technologies Program
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 1049624
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
ALLOYS
DEPOSITION
FABRICATION
HEAT TREATMENTS
MAGNETRONS
OXIDES
PARTIAL PRESSURE
PERFORMANCE
SOLAR CELLS
SPUTTERING
STRAINS
Solar Energy - Photovoltaics