Cu2Zn1–x Cdx Sn(Se1–y Sy)4 monograin powders with different x ‐ and y ‐values were prepared from binary compounds in the liquid phase of flux material (KI) in evacuated quartz ampoules. All the materials had uniform composition and p‐type conductivity. PL spectra (10 K) of the as grown Cu2Zn1–x Cdx Sn(Se)4 monograin powders showed one PL band with peak position around 0.85 eV which shifted linearly to the lower energy side with increasing Cd content. Cu2ZnSnS4 material showed asymmetrical PL band at 1.31 eV attributed to band‐to‐tail recombination. RT Raman spectra of Cu2ZnSnSe4 revealed two main peaks at 196 cm–1 and 173 cm–1 and a third less intensive peak with varying peak position in the region 231–253 cm–1. Raman spectra of Cu2ZnSnS4 showed an intensive peak at 338 cm–1 and additional peaks at 287 cm–1 and 368 cm–1. Narrow sieved fractions of grown powders were used as absorber materials in monograin layer (MGL) solar cell structures: graphite/ Cu2Zn1–x Cdx Sn(Se1–y Sy)4/CdS/ZnO. The best so far solar cell that was based on the Cu2Zn0.8Cd0.2SnSe4 had open circuit voltage 422 mV, short circuit current 12 mA/cm2 and fill factor 44%. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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In this study, we investigated the photoluminescence (PL) properties of Cu2ZnSnS4 polycrystals. Two PL bands at 1.27 eV and 1.35 eV at T = 10 K were detected. Similar behaviour with temperature and excitation power was found for both PL bands and attributed to the band-to-impurity recombination. Interestingly, the thermal activation energies determined from the temperature dependence of the PL bands coincide. With the support of the Raman results, we propose that the observed PL bands arise from the band-to-impurity-recombination process involving the same deep acceptor defect with ionization energy of around 280 meV but different Cu2ZnSnS4 phase with different bandgap energy.

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We studied the deep photoluminescence ͑PL͒ emission in polycrystalline chalcopyrite and orthorhombic AgInS 2. In both phases several PL bands were detected at 8 K. On the energy scale these deep PL bands are positioned according to a regular pattern. This is explained as being due to electron-hole recombination within very close deep donor-deep acceptor pairs, with different distances between donor and acceptor defects. The deep donor defect is an interstitial silver Ag i and the native deep acceptor defect appears to be situated at the Ag or In place. The two different crystal modifications also cause slightly different distances between donor and acceptor defects in the AgInS 2 lattice and, as a result of this, different spectral positions of the deep PL bands. It is shown that these deep localized donor-acceptor pairs can be reasonably efficient radiative recombination centers up to distances of 5.3 Å between the deep donor and the deep acceptor and, thus, up to six distinct deep PL bands are visible in AgInS 2. The deep donor-deep acceptor pair model is confirmed also by the temperature quenching experiments and by the excitation power dependences.