Dependence of Se beam pressure on defect states in CIGS-based solar cells

• Published in: Solar energy materials and solar cells Vol. 95; no. 1; pp. 227 - 230
• Main Authors: Sakurai, T., Islam, M.M., Uehigashi, H., Ishizuka, S., Yamada, A., Matsubara, K., Niki, S., Akimoto, K.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 2011; Elsevier
• Subjects: Admittance spectroscopy; Applied sciences; Cu(In,Ga)Se 2; Defect state density; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Energy; Exact sciences and technology; Molecular beam epitaxy; Natural energy; Photoelectric conversion; Photovoltaic conversion; Solar cells. Photoelectrochemical cells; Solar energy; Molecular beam epitaxy; Admittance spectroscopy; Defect state density; Cu(In,Ga)Se 2; Defect states; Defect density; Indium selenides; Solar cell; Copper selenides; Quaternary compound; Cu(In,Ga)Se; Selenium; Admittance; Gallium selenides
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2010.04.036

The influence of Se beam pressure on defect properties in Cu(In 1– x ,Ga x )Se 2 (CIGS)-based solar cells fabricated by the three-stage process was investigated by admittance spectroscopy. The Se beam pressure was varied from 1.3×10 −3 to 4.4×10 −3 Pa, at the position of the samples, by varying the Se cell temperature. The spectra for all samples show three distinct peaks denoted as α, β, and ζ with activation energies of 20, 150, and 300 meV, respectively. The trap density of ζ increased from 5×10 14 to 4×10 15 cm −3 with decrease in Se beam pressure; the trap densities of α and β did not change. These results suggest that the origin of ζ is related to the Se deficiency. The density of ζ seems to correlate with the cell efficiency. Therefore, it is important to control the Se beam pressure in order to obtain highly efficient solar cells.