Large area low cost processing for CIS photovoltaics. Final technical report

Abstract

In addition to sampling helical cores, we have also developed a loop building procedure to complement our core sampling. The combined protocol is able to sample alpha-helical proteins extremely effectively and with considerable speed. A paper describing this method is currently in preparation, DISCLAIMER DISCLAIMERPortions of this document may be illegible in electronic image products.Images are produced from the best available original document. SUMMARYCulnSe2 (CIS) and related compounds are important photovoltaic materials that have been successfully used for the fabrication of high efficiency polycrystalline thin film solar cells. Despite the impressive results achieved in the laborato~, however, commercialization of CIS based solar cells has been slow. One of the reasons for this is the fact that CIS film growth techniques employed in the research labs are based on vacuum approaches that are difficult and/or expensive to scale up. The objective of this Phase II SBIR program was to develop and demonstrate a low cost, non-vacuum deposition technique for the growth of photovoltaic-grade CIS absorber layers. The technical approach taken in this program was to develop a method that could strictly control the stoichiometric Cu/in ratio in the CIS absorbers since this stoichiometric ratio greatly affects the electrical and optical properties of this group of materials. One other consideration was to demonstrate a coating technique that can, in principle, deposit the CIS absorbers on large area substrates of 4-8 ff size. These goals were successfully reached and a patent application was submitted internationally describing the novel approach developed.The technique involves four steps; i) preparation of a Cu-in alloy powder, ii) preparation of an ink using the Cu-in powder as the pigment, iii) deposition of the ink on the selected substrate in the form of a thin precursor layer, and iv) selenization of the precursor to form the desired CIS compound.The specific tasks that were accomplished in this program were: i) A novel, low cost particle deposition technique was developed. The ability of this technique to strictly control the Cu/in ratio was demonstrated. Ability of the approach to coat large area substrates was confirmed. ii) CIS films with excellent mechanical integrity were deposited on Me/glass substrates without any peeling problems. These layers were studied by SEM and XRD. They were found to be single phase. iii) Solar cells were fabricated on the CIS layers using CdS/ZnO window layers and a total area efficiency of 10.56%, and active area efficiency of 10.9'% were demonstrated. Future work should concentrate on the densification of the compound layers for better cell performance.The results obtained in this project are important for low cost CIS based PV module production. H should be noted that, although the total worldwide PV market has now approached the $1 billion mark, the most important barrier to its explosive expansion is the cost of PV products which, at the present time, are competitive for ma...

Effect of Cu Content on Post‐Sulfurization of Cu(In,Ga)Se2 Films and Corresponding Solar Cell Performance

“…This confirms that at least the top 200 nm are fully sulfurized. The results emphasize a possibly catalyzing effect of Cu 2− x Se for sulfurization (Cu 2− x Se → Cu 2− x S → CuInS 2 ) as suggested and experimentally proposed earlier …”

Photovoltaic Technology: The Case for Thin-Film Solar Cells

“…A further degree of freedom is obtained by the partial substitution of S 2 for Se 2 (45). Other materials-oriented research efforts are directed at replacing the CdS window layer with a cadmium-free material, such as In(OH, S) (46). At present, the efficiencies of CIGS modules (30 cm by 30 cm) with integrated series connection, as fabricated in pilot production lines, are between 9 and 12% (47); this value is substantially lower than the laboratory record.…”

Post-Deposition Sulfur Incorporation into CuInSe2 Thin Films

“…With greater than 25% Cu in the film, the rate of S incorporation increases during co-evaporation of the elements [3] or post-deposition sulfurization of Cu(In,Ga)Se 2 [4]. In addition, films with small grains take up S faster than films with large grains [4,5]. In Cu-rich CuInSe 2 films on SL substrates, S incorporation has been quantitatively described as a combination of bulk and grain boundary diffusion [6].…”