Structural analysis and optical and electrical characterization of the ordered defect compound CuIn₅Se₈

Abstract

Thin polycrystalline films of the ordered defect compound CuIn 5 Se 8 and CuInSe 2 are prepared on soda lime glass substrates at temperature 623 K by coevaporation of the constituent elements. X-ray diffraction, scanning electron microscopy and energy dispersive analysis of x-rays are done on the films for structural, morphological and composition determination. The lattice constants and the anion displacements for the compounds are calculated. The deformation parameter values show that the compounds have slightly distorted tetragonal unit cells. Assuming the atomic positions, the x-ray structure factor calculations have been made and the emergence of (110) reflection in the x-ray diffraction pattern of the ordered defect compound CuIn 5 Se 8 is explained. High resistivity measured for the compound film is attributed to the compensated defect levels in it. Hot probe measurements show the conductivity of the films to be n-type. A band gap E g = 1.32 eV is observed for the compound and the increase in band gap compared to E g = 0.98 eV for CuInSe 2 is explained as a consequence of the lowering of the valence band due to weaker Se 15 (p)-Cu 15 (d) repulsion in the defect compound and electronic passivation due to 2V Cu -In Cu pairing.

Optoelectronic and low temperature thermoelectric effects in the OVC n‐CuIn3Se5 thin films

“…Thin films of CuIn 3 Se 5 were deposited on optically flat soda lime glass substrates, kept at a constant temperature of about 623 K, by three‐source co‐evaporation method. The technique used was a modified form of “Gunther's three temperature method” described elsewhere 16, 17. 99.99% pure elemental Cu and In were evaporated from two separate electrically heated molybdenum boats and 99.999% Se was evaporated from a glass crucible kept in a molybdenum basket.…”

Spin orbit and tetragonal crystalline field interaction in the valence band of CuInSe2‐related ordered vacancy compound CuIn7Se12

“…Such a reduction in the contribution of Cu d orbitals to hybridization is reasonable when we consider the diminished d-character in this Cu-deficient compound with periodic Cu vacancies [7,13]. This diminished d-character explains the decrease in the value of the spin -orbit splitting in this compound from the 0.51 eV calculated by Artus et al [24] and also the widening of the optical band gap from the ~1 eV band gap usually calculated for CIS [4,7]. The photoconductivity spectrum at room temperature for a typical CuIn 7 Se 12 film is shown in Fig.…”

“…The technique used is a modified form of 'Gunther's three temperature method' [11]. A detailed report of the preparation technique is given elsewhere [4,8].…”

“…This increase is explained by calculating the contribution of Cu d orbitals to hybridization in this Cu-deficient compound [7,13,32]. Simultaneously, the reduction in p -d hybridization due to the increased Cu vacancies in the compound can be pointed out as the reason for the increased band gap in the compound [4]. The spin-orbit splitting when determined using the method proposed by Artus et al [24] where…”

Fabrication and characterization of photovoltaic cell with novel configuration ITO/n-CuIn3Se5/p-CIS/In

“…where A is the absorbance, α the absorption coefficient, d the film thickness (0.1µm), R the reflectance and T the transmittance of the films [7].The absorbance and transmittance of the films for different wavelength are shown in figure 1a and 1b. The band gap has been determined from the equation…”