Research on polycrystalline thin-film submodules based on CuInSe{sub 2} materials. Final subcontract report, 11 November 1990--30 June 1995 [report]

R Arya, J Fogleboch, J Kessler, L Russell, S Skibo, S Wiedeman
1996 unpublished
Executive Summary Recent progress in photovoltaics has been particularly notable in several materials systems, especially in copper indium diselenide (CIS). Small area cells using this material have recently exhibited conversion efficiency in the range of I7% [1, 2] . This material system exhibits a number of important advantages. It has a very high optical absorption coefficient throughout a major portion of the solar spectrum. It can be deposited in thin films having suitable electronic
more » ... le electronic qualities on low cost substrates by a variety of methods. Modification of electronic properties such as band gap using ternary alloys has been accomplished, thus making the system versatile as well as robust. This program marks the entry of Solarex into the development of CIS based photovoltaic (PV) product. This initial effort began with the development of manufacturable deposition methods for all required thin film layers and the development and understanding of processes using those methods. It necessarily included demonstration of the potential for high conversion efficiency, evidenced by the achievement of I4.4% conversion efficiency (total area) in small cells and followed with the development of viable methods for module segment formation and interconnection. Finally, these process steps were integrated to fabricate monolithic CIS based submodules which exhibited aperture area efficiencies exceeding II%. A more important result of this program is the basis of understanding that has been established in developing this material for PV applications. This basis of understanding is absolutely necessary to address issues of manufacturability and cost which are of paramount importance to the goal of commercialization. Early in the program, it was recognized that manufacturability would be determined by successful solutions to issues of yield, reproducibility and control as much as by material and energy costs, conversion efficiency and process speed. Yield is strongly aff ected by shunt formation in modules, and shunt formation is in tum a strong function of the method used for absorber layer deposition. Issues of control and reproducibility are also strongly related to the absorber formation process. Accordingly, a significant effort was undertaken during this program to explore several alternative methods for absorber layer formation with attention to these issues. Specifically, the absorber layer formation techniques which were evaluated included: sputtering elemental precursors at low temperature followed by reaction at high temperature, a hybrid process using sputtered metallic precursors followed by reaction at high temperatures in an environment of elemental selenium, co-evaporation and concurrent reaction using elemental sources, and evaporation and/or sputtering of binary selenide precursors followed by reaction at high temperature with selenium. As a result, Solarex has identified at least one absorber formation process which is very robust to shunt formation from pinholes or point defects, tolerant of variation in processing temperature and elemental composition and capable of producing high conversion efficiency. Addendum 43 5.7. 1 Device Improvements 43 5.7.2 Submodule Improvements 43 6. Conclusions 50 J 7. References 51 ) 1 J ' �i { OF REPORT OF THIS PAGE OF ABSTRACT Unclassified Unclassified Unclassified UL NSN 7540-01 -280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. Z39-1 8 298-102
doi:10.2172/179311 fatcat:l4sbbm5rujd6bcin73fzphsssa