Investigation of combinatorial coevaporated thin film Cu2ZnSnS4. I. Temperature effect, crystalline phases, morphology, and photoluminescence Semiconducting Cu 3 BiS 3 (CBS) thin films were deposited by co-evaporation of Cu, Bi elemental metallic precursors, with in situ sulphurisation, using a quartz effusion cell. Cu 3 BiS 3 thin films were structurally characterized by XRD and FE-SEM. The chemical bonding of the ions was examined by XPS. As deposited films were demonstrated for metal-semiconductor-metal near IR photodectection under lamp and laser illuminations. The photo current amplified to three orders and two orders of magnitude upon the IR lamp and 60 m W cm À2 1064 nm IR laser illuminations, respectively. Larger grains, made up of nano needle bunches aided the transport of carriers. Transport properties were explained based on the trap assisted space charge conduction mechanism. Steady state detector parameters like responsivity varied from 1.04 AW À1 at 60 m Wcm À2 to 0.22 AW À1 at 20 m Wcm À2 . Detector sensitivity of 295 was found to be promising and further could be tuned for better responsivity and efficiency in utilization of near infra-red photodetector. V C 2014 AIP Publishing LLC. [http://dx.

Earth abundant alternative chalcopyrite Cu 2 CoSnS 4 (CCTS) thin films were deposited by a facile sol−gel process onto larger substrates. Temperature dependence of the process control of deposition and desired phase formations was studied in detail. Films were analyzed for complete transformation from amorphous to polycrystalline, with textured structures for stannite phase, as reflected from the X-ray diffraction and with nearly stoichiometric compositions of Cu:Co:Sn:S = 2:0:1:0:1:0:4:0 from EDAX analysis. Morphological investigations revealed that the CCTS films with larger grains, on the order of its thickness, were synthesized at higher temperature of 500 °C. The optimal band gap for application in photovoltaics was estimated to be 1.4 eV. Devices with SLG/CCTS/Al geometry were fabricated for real time demonstration of photoconductivity under A.M 1.5 G solar and 1064 nm infrared laser illuminations. A photodetector showed one order current amplification from ∼1.9 × 10 −6 A in the dark to 2.2 × 10 −5 A and 9.8 × 10 −6 A under A.M 1.5 G illumination and 50 mW cm −2 IR laser, respectively. Detector sensitivity, responsivity, external quantum efficiency, and gain were estimated as 4.2, 0.12 A/W, 14.74% and 14.77%, respectively, at 50 mW cm −2 laser illuminations. An ON and OFF ratio of 2.5 proved that CCTS can be considered as a potential absorber in low cost photovoltaics applications.

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Thin films of CuIn 1−x Al x Se 2 (CIAS) were grown on the flexible 10 micrometer thin stainless steel substrates, by dc co-sputtering from the elemental cathodes, followed by annealing with modified selenization. CuInAl alloyed precursor films were selenized both by noble gas assisted Se vapor transport in a tubular furnace and vacuum evaporation of Se in an evaporation chamber. CIAS thin films were optimized for better adhesion. X-ray diffraction, scanning electron microscopy, and UV-visible absorption spectroscopy were used to characterize the selenized films. The composition of CIAS films was varied by substituting In with Al in CuInSe 2 (CIS) from 0 ≤ x ≤ 0.65 (x = Al/Al+In). Lattice parameters, average crystallite sizes, and compact density of the films, decreased when compared to CIS and (112) peak shifted to higher Bragg's angle, upon Al incorporation. The dislocation density and strain were found to increase with Al doping. Solar cells with SS/Mo/CIAS/CdS/iZnO:AZnO/Al configuration were fabricated and were tested for current-voltage characteristics for various 'x' values, under Air Mass 1.5 Global one sun illumination. The best CIAS solar cell showed the efficiency of 6.8%, with x = 0.13, E g = 1.17 eV, fill factor 45.04, and short circuit current density J sc 30 mA/cm 2 .