Sputtered Cd1-xZnxTe films for top junctions in tandem solar cells

• Published in: Solar energy materials and solar cells Vol. 86; no. 4; pp. 551 - 563
• Main Authors: SUNG HYUN LEES, GUPTA, Akhlesh, SHANLI WANG, COMPAAN, Alvin D, MCCANDLESS, Brian E
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 01.04.2005
• Subjects: Applied sciences; Energy; Equipments, installations and applications; Exact sciences and technology; Natural energy; Photovoltaic conversion; Solar cells. Photoelectrochemical cells; Solar energy; Tandem solar cell; Scanning electron microscopy; Magnetron; Resistivity; Alloys; Photoluminescence; Polycrystal; X ray diffractometry; Preferred orientation; Optical absorption; Sputtering
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2004.09.008

Cd1-xZnxTe alloy films with 1.6 and 1.7eV band gaps were deposited by RF magnetron sputtering from targets made either of mixed powders or alloys of CdTe and ZnTe (25% and 40%). High-quality polycrystalline films with the (111) preferred orientation were obtained. The films were characterized using X-ray diffraction (XRD), scanning electron microscopy, resistivity, optical absorption, Raman, and photoluminescence. The EDS, XRD, and optical absorption analysis indicated that the x-value of the as-grown films were typically 0.20 and 0.30 for films sputtered from 25% and 40% ZnTe containing targets, respectively. The as-deposited alloy films exhibit quite low photovoltaic performance when used to make cells with CdS as the hetero-junction partner. Therefore, we have studied various post-deposition treatments with vapors of chlorine-containing materials, CdCl2 and ZnCl2, in dry air or H2/Ar ambient at 390 deg C. The best performance of a Cd1-xZnxTe cell (, ) was found for treatment with vapors of the mixed CdCl2+0.5%ZnCl2 in an H2/Ar ambient after pre-annealing at 520 deg C in pure H2/Ar.