Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7117350 | Materials Science in Semiconductor Processing | 2018 | 6 Pages |
Abstract
CuGaxIn1âxSe2 (CIGS) (xâ¯=â¯0, xâ¯=â¯0.3 and xâ¯=â¯1) absorber layers were deposited onto transparent conducting oxide (SnO2) substrates using close-spaced vapor transport technique (CSVT). The aim of this work was to assess the quality of CIGS absorber films with various gallium contents. Composition found by Energy Dispersive Spectroscopy (EDS) showed that the investigated samples were Cu-poor and CuGa0.3In0.7Se2 thin film had a composition close to 0.3 as planned. The structural properties were investigated by X-ray diffraction analysis (XRD) and Raman spectroscopy, while optical properties were investigated by measuring transmittance and photoluminescence spectroscopy. It was found that all investigated samples crystallize with (112) as a preferential crystallographic direction. The shift of the XRD peaks towards a higher value of 2θ with the increase of Ga composition was observed. The grain size determined from the width of 112 XRD peak was within 40-75â¯nm range with no clear correlation with Ga content. Raman spectra of samples with xâ¯=â¯0 and 0.3 featured mainly a peak assigned to the A1 mode at about 175â¯cmâ1. In CuGaSe2 the secondary Cu2Se phase was detected both by XRD and Raman. The band gap as evaluated by optical transmission measurement is shifted towards lower than expected values due to substantial defect-related bands broadening. A large concentration of defects in the samples was also confirmed by low or absent PL signal in the vicinity of the bandgap, while the emission due to deep defects was prevailing in the spectrum. The optoelectronic properties as indicated by photoluminescence have to be improved if CSVT method of absorber preparation is to be used more widely in photovoltaics.
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Authors
Houda Tassoult, Abdesselam Bouloufa, Marek Pawlowski, Malgorzata Igalson,