Formation Of CuIn Research Articles

Polyol Mediated Solvothermal Synthesis and Characterization of CuIn(1−x)GaxS2 Nanocrystals

Gallium-substituted copper indium sulfide (CuIn(1−x)GaxS2) nanoparticles have been synthesized by a convenient solvothermal method without usage of surfactants or toxic reductants such as hydrazine. Thiourea, sodium hydroxide, CuCl2·2H2O, InCl3 and GaCl3 were used as starting materials and ethylene glycol as solvent and reducing agent. The reactions were performed at 200 °C for 16 h. Effect of sodium hydroxide on the reaction products is analyzed. The powders are mainly characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, BET surface area measurements and UV–Vis absorption spectroscopy. The results show that the gallium is successfully incorporated into the chalcopyrite crystal structure. The homogeneous powders obtained are constituted of nanoparticles with sizes in the range 20–30 nm and exhibit a specific surface area close to 65 m2/g. Further, the possible mechanism for the formation of CuIn(1−x)GaxS2 nanocrystals is explained. The optical band gap energies of the nanoparticles were in the range 1.48–1.75 eV.

Formation of CuIn(SxSe1−x)2 microcrystals from CuInSe2 nanoparticles by two step solvothermal method

Here we introduced a two-step reaction to synthesize highly crystalline CuIn(S1−xSex)2 (CuInSSe) microcrystals from CuInSe2 nanocrystals. CuInSSe micro particles can be obtained without toxic selenization or sulfurization process and the composition of sulfur and selenium can be easily controlled by varying the amount of precursor at different stages of the reactions. This synthetic route allows a technique that is simple and non-toxic together with the possibility of tuning the composition. XRD, HRTEM and SAED analysis of the final product confirmed the pure phase formation of CuInSSe. EDAX analysis shows the compositions of the final product matched with CuInSSe and the compositions of the product can tune by the reaction parameter. UV–Vis absorption spectra reveals a clear blue shift due to an increase in band gap with the increase of sulfur content. Initial photocurrent response suggests its possibility to be used as absorber materials in thin film solar cells.

Formation of CuIn(1-x)GaxSe2 (CIGS) by Electrochemical Atomic Layer Deposition (ALD)

The formation of CuIn(1-x)GaxSe2 (CIGS) by electrochemical atomic layer deposition (E-ALD) is reported. Two different CIGS E-ALD cycle programs were investigated. The first consisted of the sequential deposition of alternating atomic layers (AL) metal and Se. That is, AL of Cu, In and Ga were alternated with AL of Se, in what is referred to as a quaternary CIGS program. The second was a superlattice program, composed of differing numbers of the binary compound cycles repeated in a period. The use of the superlattice program allowed better control of the overall stoichiometry. Electron probe microanalysis was used to characterize deposit compositions. A discussion of how variations in the deposition programs affected the resulting deposit compositions is presented. Deposits were formed with the classic CIGS stoichiometry (CuIn0.7Ga0.3Se2) using the superlattice program. XRD patterns for the E-ALD deposited chalcopyrite CIGS are reported as deposited, no annealing.

CuIn (Se,S) 2 based photovoltaic cells from one-step electrodeposition

The formation of CuIn (Se,S)2 films for application in photovoltaic devices by post-deposition treatments of electrodeposited pre-cursors is described. The polycrystalline CuInSe2 (CIS) pre-cursor layers were prepared by the one-step electrodeposition (ED) method on molybdenum-coated soda lime (SL) glass substrates. Growth was performed from low concentration buffered baths containing CuSO4, In2(SO4)3 and SeO2 with Li2SO4 electrolyte. As deposited films were amorphous and required recrystallization by annealing in H2Se or H2S prior to device processing. Reaction in flowing H2Se produced random oriented CuInSe2 films which resulted in devices with low conversion efficiencies of only~3%. Annealing in flowing H2S led to partial replacement of the selenium in the CuInSe2 film with sulfur, determined by XRD and EDS to produce CuIn(Se,S)2 quaternary alloys. Devices processed from CuIn(Se,S)2 films showed improved J-V characteristic with conversion efficiencies of ~6.4%. Key words: CuInSe2, CuIn(Se,S)2, absorber layers, electrodeposition, pHydrion buffer, photovoltaic cells.

Real-time Investigations on the Formation of CuIn(S,Se)2 while annealing precursors with varying sulfur content

AbstractCIS based chalcopyrite absorber materials are usually substituted in the cation and anion lattice to yield mixed pentanary crystals with the general composition Cu(In,Ga)(Se,S)2 to achieve an optimised adaptation of the semiconductor bandgap to the terrestrial solar spectrum. Real-time investigations during the annealing of stacked elemental layers (SEL) of sputtered metals Cu and In and evaporated chalcogens S and Se with varying ratios were performed by angle-dispersive time-resolved XRD (X-ray diffraction) measurements. After qualitative phase analysis the measured powder diagrams were quantitatively analysed by the Rietveld method, the phases formed determined and their reaction kinetics obtained. Ternary indium and copper sulfoselenides form by the sulfoselenisation of the intermetallic alloy yielding different educts for the chalcopyrite formation with varying sulfur content. For S/(S+Se) ≥ 0.5 the formation of the chalcopyrite CuIn(S,Se)2 is similar to the crystallisation path of CuInS2. With increasing amount of selenium (S/(S+Se) = 0.25) different ternary sulfoselenides contribute to the semiconductor formation. For small amounts of sulfur, i.e. S/(S+Se) ≤ 0.1, the chalcopyrite crystallisation proceeds comparable to the one observed for sulfur-free Cu-In-Se precursors. The formation of CuIn(S,Se)2 is accelerated and proceeds mainly after the peritectic decomposition of Cu(S,Se) to Cu2(S,Se). The sulfur content determines the crystallisation temperature of the semiconductor because Cu(S,Se) decomposes at higher temperatures with increasing sulfur. Upon heating S ↔ Se exchange reactions take place in the Cu-S-Se and Cu-In-S-Se system.

The Formation of CuIn(S,Se)2 Thin Film Solar Cell Absorbers from Electroplated Precursors

AbstractIn this article structural properties as well as morphological aspects of CuIn(S,Se)2 thin film solar cell absorbers, produced by annealing of electroplated precursors, are discussed. Real-time X-ray diffraction (XRD) experiments while precursor annealing have shown, that a reduced amount of electrodeposited selenium is the key parameter to realize a chalcopyrite formation mechanism similar to the one known for sputtered stacked elemental layer (SEL) precursors. Absorber layers processed from precursors produced by simultaneous electrodeposition of copper, indium and selenium show a preferable absorber morphology with an average grain size on the micrometer scale when the electrochemically deposited amount of selenium is reduced to [Se] / [In] = 0.1. The amount of selenium, missing for the formation of a stoichiometric chalcopyrite, was deposited in a second process step prior to precursor annealing. Solar cells produced from these absorbers show light conversion efficiencies up to 10%.

Influence of the stacking order on structural features of the Cu‐In‐Ga‐Se precursors for formation of Cu(In,Ga)Se 2 thin films prepared by thermal reaction of InSe/Cu/GaSe alloys to elemental Se vapor and diethylselenide gas

A novel partway for the fabrication of copper-indium (gallium) diselenide has been developed. This two-stage process consists of the formation of Cu-In-(Ga)-Se precursors and subsequent selenization to form CuIn(Ga)Se2. In this work, we have investigated and compared the possible interactions in Cu-In-Ga-Se systems, using sequentially stacked precursors premixed with Se, in order to get a better understanding of the Cu(In,Ga)Se2 thin film formation. Comparison of these SEM micrographs clearly revealed that the surface morphologies and hence surface roughness of the resulting Cu(In,Ga)Se2 absorber films were significantly influenced by the structure of the precursor films prior to selenization. XRD analyses revealed the presence of a graded CuIn1-xGaxSe structure, irrespective of the stacking order during the precursor formation step for samples selenized using elemental Se vapor. It was established that distinct from the case of using Se vapor, a single-phase Cu(In,Ga)Se2 films were obtained by diethylselenide (DESe) selenization from Cu-In-Ga metal precursors premixed Se irrespective of the stacking order during the precursor formation step. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Formation of CuIn(S,Se) 2 thin film by thermal diffusion of sulfur and selenium vapours into Cu–In alloy within a closed graphite container

The formation of CuIn(S,Se) 2 thin films by thermal diffusion of sulfur (S) and selenium (Se) vapours into co-sputtered Cu–In alloy within a closed-space graphite container is reported. All films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Four-point-probe and hot-probe measurements. Cu–In alloy films with composition varying from Cu-rich to In-rich were deposited. The synthesized In-rich films yielded CuIn 5(S,Se) 8 spinel compound which gradually transformed into a single phase CuIn(S,Se) 2 as the film composition approached the Cu-rich region. The morphology of the CuIn 5(S,Se) 8 was found to differ from the stoichiometric and Cu-rich CuIn(S,Se) 2 as observed from SEM. EDX composition analysis of the films showed a Cu/In ratio varying from 0.36 to 1.54 and a (S+Se)/(Cu+In) varying from 0.97 to 1.32. The amount of S incorporated in the films was found to differ with changes in the composition. The resistivity of the films ranged between 10 −1 and 10 7 Ω cm and it strongly followed the change in the alloy film composition.

Formation of CuIn(Ga)Se2 Thin Films by Selenization and Application to Solar Cells

Preparation conditions of device-quality CuInSe2 (CIS) and CuIn1-xGaxSe2 (CIGS) thin films were studied. We formed CIS and CIGS films by annealing different types of precursor films, such as Gu/In stacked films and Cu–In–Se co-deposited films, under H2Se atmosphere. We obtained CI(G)S films with large grain size using precursors prepared at 200°C. The grain sizes of CI(G)S film using stacked precursors were larger than those using co-deposited precursors. Use of co-deposited precursors reduced formation of MoSe2 at Mo/CI(G)S boundary during selenization process. Fill-factor (FF) exceeding 0.7 was obtained for CIS cells using co-deposited precursors prepared at substrate temperature of 200°C.