Title :
An improved understanding of efficiency limiting defects in polycrystalline CdTe/CdS solar cells
Author :
Rohatgi, A. ; Ringel, S.A. ; Sudharsanan, R. ; Chou, H.C.
Author_Institution :
Sch. of Electr. Eng., Georgia Inst. of Technol., Atlanta, GA, USA
Abstract :
Efficiency-limiting mechanisms associated with CdS substrates, CdCl2 treated CdTe films, and Cu/Au contacts were investigated. It was found that thermal treatment prior to CdTe deposition removed the oxygen-related defects from the CdS films. However, it also created nonuniform and Cd deficient CdS surface, resulting in an optimum temperature of 450°C. Growth of CdTe films on the CdS under Te-rich conditions enhanced the interdiffusion between CdTe and CdS and reduced the CdTe bandgap to 1.47 eV, whereas growth of CdTe films under Cd-rich conditions retained the CdTe bandgap at 1.5 eV by reducing the interdiffusion. It was found that use of thinner CdS (1000 Å instead of 2000 Å) films increased the cell efficiency from 9.7% to 10.3% by increasing the JSC from 22.4 to 24.19 mA/cm2
Keywords :
II-VI semiconductors; cadmium compounds; chemical interdiffusion; crystal defects; solar cells; 9.7 to 10.3 percent; CdCl2; CdS; CdS substrates; CdTe bandgap; CdTe film growth; CdTe-CdS solar cells; Cu-Au contacts; efficiency limiting mechanisms; interdiffusion; oxygen-related defects; polycrystalline solar cells; thermal treatment; Annealing; Copper; Etching; Glass; Gold; Molecular beam epitaxial growth; Photonic band gap; Photovoltaic cells; Substrates; Temperature;
Conference_Titel :
Photovoltaic Specialists Conference, 1991., Conference Record of the Twenty Second IEEE
Conference_Location :
Las Vegas, NV
Print_ISBN :
0-87942-636-5
DOI :
10.1109/PVSC.1991.169351
