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

Single Second Laser Annealed CuInSe2 Semiconductors from Electrodeposited Precursors as Absorber Layers for Solar Cells

Cu(In,Ga)Se2 (CIGSe) is a polycrystalline absorber layer in thin film solar cells with solar conversion efficiencies exceeding 20%. High temperature annealing for periods of minutes to hours is currently required to convert amorphous or nanocrystalline precursor material into high quality Cu(In,Ga)Se2 absorber layers. In this work, we perform the critical annealing step, using a 1064 nm laser, on electrodeposited precursor layers containing Cu, In, and Se, for times of 0.3-60 s thus synthesizing CuInSe 2 absorber layers. An annealing time of 1 s is found to be sufficient to remove elemental concentration gradients in the bulk of the layer and to increase the average implied crystallite size (crystal coherence length, as determined by X-ray diffraction, XRD). Therefore the rate-determining step in producing higher quality layers with short annealing times is the rate of grain growth and not atomic diffusion. Optoelectronic analysis of the absorber layers revealed p-type doping with improved radiative recombination compared to the precursors. Laser annealed CuInSe2 layers did not produce working photovoltaic devices. This is first attributed to a loss of Se that occurs during laser annealing, resulting in detrimental substoichiometric quantities of Se in the absorber. Second, the likely presence of a thick surface layer of the CuIn3Se5 phase is expected to detrimentally impact device performance. These findings must be addressed if annealing times of the CuInSe2 absorber layer are to be reduced to seconds. \ua9 2013 American Chemical Society