Photoluminescence of CuInS2 single crystals grown by traveling heater and chemical vapor transport methods

Photoluminescence of CuInS2 single crystals grown by both the traveling heater method (THM) and chemical vapor transport (CVT) has been investigated at 4.2, 78, and 300 K. Intense emission in the near-band-edge region caused by free and bound excitons has been detected for both types of crystals. Taking into account the energy position of the luminescence line of the ground (n = 1) and first excited (n = 2) states, the binding energy for free A excitons has been estimated to be about 19.7 and 18.5 meV for CuInS2 grown by CVT and THM, respectively

In situ transmission electron microscopy studies of radiation damage in copper indium diselenide

The ternary semiconductor, CuInSe2 (CIS), is a promising semiconductor material for use in photovoltaic applications. Of particular interest is the high tolerance of this material to bombardment by energetic particles. This is of particular importance for photovoltaic applications in outer space where the lifetime of CIS-based solar cells has been found to be at least 50 times that of those based on amorphous silicon. In this paper we report on studies of the build-up of radiation damage in CIS during irradiation with Xe ions in the energy range 100–400 keV. Room temperature experiments indicate that dynamic annealing processes prevent the build-up of high levels of damage. However, for irradiation at a temperature of 50 K, the behaviour changes drastically with the material amorphising at low fluences. This effect is discussed in terms of defect mobility

Effects of D+ implantation of CIGS thin films through a CdS layer

Cu(InGa)Se2 thin films coated with a 30 nm CdS layer were implanted with doses of 1014–1016 cm−2 of 2.5 keV D+ at room temperature. Implanted and non-implanted areas of the films were characterised using low-temperature photoluminescence (PL). A broad band (A) at 1.07 eV, attributed to the band-tail recombination, dominated the PL spectra from the non-implanted material. Implantation of D+ generated four new transitions in the PL spectra: 3 low-energy peaks; and a dominant peak at 1.10 eV. The blue shift of the 1.10 eV band with excitation power rise was shown to be only half that of band A. This was attributed to the passivating effects of D+ on the amplitude of the band-tail potential fluctuations

Copper indium diselenide: crystallography and radiation-induced dislocation loops

Copper indium diselenide (CIS) is a prime candidate as the absorber layer in solar cells for use in extraterrestrial environments due to its good photovoltaic efficiency and ability to resist radiation damage. While CIS-based devices have been tested extensively in the laboratory using electron and proton irradiation, there is still little understanding of the underlying mechanisms which give rise to its radiation hardness. To gain better insight into the response of CIS to displacing radiation, transmission electron microscope samples have been irradiated in situ with 400 keV Xe ions at the Intermediate Voltage Electron Microscope facility at Argonne National Laboratory, USA. At room temperature, dislocation loops were observed to form and grow with increasing fluence. These loops have been investigated using g  ·  b techniques and inside/outside contrast analysis. They have been found to reside on {112} planes and to be interstitial in nature. The Burgers vector were calculated as b  = 1/6 221. The compositional content of these interstitial loops was found to be indistinguishable from the surrounding matrix within the sensitivity of the techniques used. To facilitate this work, experimental electron-diffraction zone-axis pattern maps were produced and these are also presented, along with analysis of the [100] zone-axis pattern

Characterization of polycrystalline Cu(In,Ga)Te2 thin films prepared by pulsed laser deposition

Thin films of the chalcopyrite compound CuGaXIn1-XTe2 (0=<X=<1) have been prepared by pulsed laser deposition (PLD) of prereacted material onto glass substrates. The structural and optical properties of these films have been investigated using the techniques of X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), Rutherford back scattering (RBS), transmittance (T), reflectance (R). Electrical characterization was performed using Hall and resistivity measurements, using the Van der Pauw technique at 300 K. The composition of the laser-deposited films was found to closely match that of the target materials and the XRD showed them to be single phase with the chalcopyrite structure and a preferred orientation along the (112) plane. The spectral dependence of the refractive index n and absorption coefficient alpha of the Cu(In,Ga)Te2 thin films were determined using rigorous expressions for transmission and reflection in an air/film/substrate/air multilayer system. The CuGaXIn1-XTe2 films had optical absorption coefficients of order 104 cm-1 and the energy gaps observed in these films increased from 0.96 to 1.32 eV with increasing Ga content