Electrochemical Atomic Layer Deposition of CuIn_(1-x)Ga_xSe₂on Mo Substrate

Abstract

The chalcopyrite CuIn (1-x) Ga x Se 2 (CIGS) thin films were grown on Mo substrate by electrochemical atomic layer deposition (E-ALD) of superlattice sequencing 2InSe/2GaSe/1CuSe, recently developed on model Au surface by Stickney and coworkers (J. Electrochem. Soc. 161, D141 (2014)). The cyclic voltammetry studies were conducted on copper, selenium, indium and gallium on molybdenum substrate and CIGS films were grown by different numbers of superlattice sequencing. The deposited films were examined for phase and microstructure formations by X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning tunneling microscopy (STM) and energy dispersive spectroscopy (EDS). The XRD pattern corresponded to those of chalcopyrite crystalline phase of CIGS and the crystallite size increased with the number of cycles or periods of whole superlattice sequencing increased. The SEM and STM results were in line with those of XRD by showing that the particle size increased as the number of E-ALD cycles increased. The EDS results revealed the CIGS with near stoichiometry. Finally, the deposited E-ALD films were shown to be photoelectrochemically active with p-type conductivity. We wish to describe the preparation of CuIn (1-x) Ga x Se 2 (CIGS) by means of electrochemical atomic layer deposition (E-ALD) on Mo substrate of each component element in aqueous solutions at ambient laboratory conditions and to show that the resulting films are photoelectrochemically active with p-type conductivity.Solar energy, the prominent energy source of the universe could be properly utilized for the current increasing trends for energy needs of our entire planet. Alternate energy production technologies like thin film solar cells have been successfully competing traditional energy production methods raised over recent years.1-3 The chalcopyrite Cu(In,Ga)(Se/S) 2 modules of thin films are the promising tool in commercially manufacturing thin film photovoltaic (PV) technologies available in PV market today. 4 The chalcopyrites CIGS are compound semiconductors which are largely known for high absorption coefficient (1 × 10 5 cm −1 ) at photons above the bandgap. 5 The Ga substitution can make the compound with highly adjustable bandgap (1.04 eV for CuInSe 2 (x = 0) to 1.68 eV for CuGaSe 2 (x = 1)) 6 with high stability under high energy irradiation. 7,8 The bandgap of the material is more closely found with the optimum conversion efficiency range (1.4 ∼ 1.5 eV) of solar radiation.9 Because of these properties, it attracted considerable interests by the researchers and industrialists to use CIGS as light-absorbing materials for thin film photovoltaic cells.7-10 Recent works on CIGS have achieved the power conversion efficiency up to 22.6% in laboratory scale. [20][21][22][23] These synthesis methods need larger investment in machinery and workspace which involve highly complicated instruments. The difficulties are with the problems in maintaining the laboratory conditions, complicated procedures and unusual release of heat and toxic byprod...

Electrochemical Atomic Layer Deposition of CuInSe2 on Au Surface

“…The chemical composition of the film was determined by energy dispersive X‐ray spectroscopy (EDS, Horiba EX‐250; Minami, Kyoto, Japan). Topography of the film was investigated by scanning tunneling microscopy (STM, Agilent 5100 AFM/SPM; Santa Clara, CA, USA) with electrochemically etched tungsten tip . The film thickness from side‐view image was studied by high‐resolution scanning electron microscope (HR‐SEM, Hitachi S‐4800; Chiyoda, Tokyo, Japan).…”

“…A handful of semiconductor compounds have been synthesized by E‐ALD techniques, including CIS and CIGS . Wang et al .…”

“…have reported CIS on Au surfaces . We have established a successful sequence of steps to make CIGS and CIGS/CdS on Mo substrates by adopting this technique. The previous report on CIS by Stickney et al .…”

Mo/CIGS/CdS Structures by E‐ALD

“…1 After CIGS films were successfully grown on Mo foil, the CdS binary compound deposition steps were carried out over the top of CIGS/Mo foil. 1 After CIGS films were successfully grown on Mo foil, the CdS binary compound deposition steps were carried out over the top of CIGS/Mo foil.…”

“…1 CIGS is one of the promising candidates for highefficiency and low-cost solar power generation thin film photovoltaic materials. 1 CIGS is one of the promising candidates for highefficiency and low-cost solar power generation thin film photovoltaic materials.…”