Abstract
Se-containing precursor films with two different compositions were prepared by magnetron sputtering from and targets, and then were selenized using Se vapor. The effects of precursor composition and selenization temperature on the film properties were investigated. The results show that Se phase plays a critical role in film growth and electrical properties of CIGS films. The Cu-rich films exhibit different surface morphology and better crystallinity, as compared to the Cu-poor films. All the CIGS films exhibit p-type conductivity. The resistivity of the Cu-rich films is about three orders of magnitude lower than that of the Cu-poor films, which is attributed to the presence of p-type highly conductive Se phase.
Highlights
Cu(In1−xGax)Se2 (CIGS) thin films have received considerable attention in recent years because of their application in solar cells, which have many advantages in high conversion efficiency [1, 2], the possibility of low-cost production [3, 4], and long-term stability [5, 6]
The bandgap of chalcopyrite CIGS absorber could vary from 1.04 eV in CuInSe2 to 1.68 eV in CuGaSe2 by substituting indium for gallium
The CIGS films with higher gallium concentration show a significant loss of efficiency relative to lower gallium content films [12]
Summary
Cu(In1−xGax)Se2 (CIGS) thin films have received considerable attention in recent years because of their application in solar cells, which have many advantages in high conversion efficiency [1, 2], the possibility of low-cost production [3, 4], and long-term stability [5, 6]. The world-record efficiency for small-area CIGS-based thin film solar cells has recently surpassed 20% [7]. A variety of processing techniques have been developed to prepare high quality CIGS thin films. The two most reported processes are the coevaporation from elemental sources and the selenization of metallic precursors. The selenization of metallic precursors is a two-stage process, which involves the deposition of Cu-In-Ga metallic precursors in the first step followed by their selenization using H2Se gas or Se vapor [16]. The presence of low-melting metal indium in Cu-In-Ga metallic precursors could always result in rough morphologies of the CIGS films and loss of indium from films during the ramp-up and selenization stages [17, 18]. The effects of precursor compositions and selenization temperature on the film properties were investigated
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