Optical and electrochemical properties of CuInSe2 and CuInS2-CuInSe2 alloys

Abstract

showed a significant shift in the J-V curves on both branches. In Fig. 2 we display a plot of In J /V 2 vs l/V for a sample containing 6% manganese in fields of 0 and 5 T. For com· parison, we show in Fig. 3 the difference of the tunneling current with and without a 5·T field.The most elegant way to obtain a value for the relative change of the barrier height is by taking the voltage ratio at a constant value of In I /V2. Thus, wee1iminate all dimension· al uncertainties (thickness, electrically active area). Referring to Eq. (I j, it is easily seen that(2)We consequently have chosen an arbitrary value In 1/ V 2 = -12 in Fig. 2. The appropriate values for 1/Vat 0 and 5 T yield (if>H",o/if>H=o)-:::=l -0.67ilV H =0 = 1 -0.67(0.005/0.249) = 0.99. If it is estimated, in addition, that the barrier height if> is 1 eV,6 one obtains immedi· ately the lowering of ¢> to be of 10 ± 5 meV, i.e., the overall Zeeman splitting is 20 ± 10 me V for the conduction band.Therefore, in this compound at 4.2 K, the effective g value for the conduction band is of the order of 30, 15 times larger than for a nonmagnetic semiconductor with an s-like conduction band. The agreement with the results from magnetooptical experiments is excellent, and confirms the validity of the Fowler-Nordheim expression for high electric fields in these compounds.Our work demonstrates that the conduction-band splitting in semi magnetic semiconductors in the presence of an externally applied magnetic field can be observed directly by a simple transport measurement. Spurious effects other than the enhancement of the effective g value through the presence of the Mn dopant may be ruled out because the field shift disappears in pure CdTe. Furthermore, we have shown that Cd l _ x Mn" Te may be fabricated into simple heterostructures in which magnetointernal field emission is observable.The fundamental optical transitions in single crystals ofCulnS 2x Se 2 _ 2x alloys have been studied by electrolyte electroreflectance (EER) spectroscopy. The band gap of the alloys increases nonlinearly with increasing sulphur content corresponding to a bowing parameter 0.14_ The ftatband potential derived from the EER spectra is in excellent agreement with differential capacitance measurements and determined as -0.350 V versus the saturated calomel electrode. CuInS 2x Se 2 _ 2>: liquid junction solar cells are reported that exhibit a long wavelength cutoff in the spectral response matching the EER data.The group I-III-VI 2 compound semiconductors, j.e., the sulphides and selenides, have attracted considerable interest recently. Referring to the position of the fundamental optical transition as well as the extremely steep absorption edge and the high absorption coefficient, these materials should be of particular interest for solar cell applications. For instance, CuInSe 2 /CdS thin-film cells have been fabricated with power conversion efficiencies exceeding 10%. 1 The reliability and performance are strongly affected by the high density of native defects, usually observed in bulk c...

Copper Indium Selenides and Related Materials for Photovoltaic Devices

“…The bandgap dependence on composition has been reported by several researchers, with the reported optical bowing parameters varying from 0 to 0.88. [145][146][147] There is substantially better agreement between a larger number of studies of the mixed-anion alloy CuGa(Se X S 1-X ) 2 that the optical bowing parameter in that system is zero. 148, and references therein It has been argued that the bond-alternation, which leads to optical bowing in mixed-cation ternary chalcopyrite alloys, does not occur in the mixedanion alloys, 149 and that the bowing parameter therefore should vanish in CuIn(Se X S 1-X ) 2 , as reported by Bodnar and co-workers.…”

Influence of different sulfur to selenium ratios on the structural and electronic properties of Cu(In,Ga)(S,Se)2 thin films and solar cells formed by the stacked elemental layer process

“…In Figure 7(b), three dotted lines symbolize theoretical dependence of the E g (Refs. 4, 5, and [15][16][17] ) on the SSSe ratio for different GGI ratios. For comparison, the E g values obtained from the PL and the EQE data are shown.…”

Processing of CuInSe2-Based Solar Cells: Characterization of Deposition Processes in Terms of Chemical Reaction Analyses. Final Report, 6 May 1995 - 31 December 1998

“…The bandgap dependence on composition has been reported by several researchers, with the reported optical bowing parameters varying from 0 to 0.88 [123][124][125]. There is substantially better agreement between a larger number of studies of the mixed-anion alloy CuGa(SeXS1-X)2 that the optical bowing parameter in that system is zero [126, and references therein].…”