Coevaporated Cu–In films as precursors for solar cells

Abstract

We investigate Cu–In thin films used as precursors for the production of CuInS2 and Se2 solar-cell absorber material via reactive annealing. The films are produced by coevaporation of Cu and In onto glass substrates and are characterized by means of Rutherford backscattering and x-ray diffraction (XRD). The interplay of phase composition, morphology, and surface topography is studied as a function of chemical composition, substrate temperature, and annealing processes. The analysis of the XRD data is based on known crystallographic data for the phases Cu7In3 (δ phase), Cu16In9 (η′ phase), Cu11In9, and In. Refined crystallographic data for CuIn2 are presented, and the low-temperature modification of Cu16In9 (η-phase) is investigated by means of bulk powder samples. These data and the inclusion of texture effects allow us to perform a complete RIETVELD type analysis of the Cu–In precursors. It is shown that, in contrast to sequentially evaporated films, all known Cu–In equilibrium phases can be formed during film deposition. These are Cu7In3, Cu16In9, Cu11In9, and CuIn2. Moreover, it is found that single-phase films of all these phases can be produced. Film roughness is shown to increase with deposition temperature and In content. The results presented offer new prospects for sulfurization and selenization processes in solar-cell production.

Chemical synthesis of Cu(In) metal inks to prepare CuInS2 thin films and solar cells

“…The XRD pattern shown in Fig. 1(c) elucidates that the Cu-In nanoparticles contain the two main phases of In (tetragonal, JCPDS-65-9682) and Cu 11 In 9 (monoclinic, JCPDS-65-4963), which is consistent with the previous report that stable component phases of Cu-In alloy above 150 • C are mainly In and Cu 11 In 9 [17]. In fact, we obtain the two component phases at a relative lower temperature of 140 • C. The obtained Cu-In nanoparticles are bigger in sizes due to the inter-diffusion of Cu and In nanoparticles [18], as indicated from the SEM image of a Cu-In metal film in Fig 4(a).…”

Real-time studies of phase transformations in Cu–In–Se–S thin films

“…All three types of samples originally consisted of CuIn 2 and Cu, as was already reported in Refs. [7,10] due to the reaction Cu solid +2In solid -CuIn 2 taking place above À33 1C [5]. In accordance with the overall composition of the films, the concentration of free Cu is decreasing with the decreasing Cu/In ratio.…”

“…These phases may be metastable modifications of the Z-Cu 16 In 9 phase and its high-temperature modification Z 0 . In a recent work, Gossla et al [7] were able to prepare all phases which are stable at room temperature using co-evaporation of Cu x In layers. Using in situ high-energy powder diffraction, Brummer et al [8] have investigated the Cu-In phase transformations with 60 sec time resolution.…”

The terahertz emission and photoelectron spectroscopy study of CuInS₂ thin films

“…CuInS 2 (CIS) with the band gap value of 1.5 eV and its high absorption coefficient of almost 10 5 cm −1 is representing an important class of the recently developed light absorbers for highly efficient and lowcost solar cells [1][2][3]. Recent studies have shown that CIS solar cell efficiency ranges from 10.2 to 12.3% [4][5].…”

“…One of the most commonly used methods is a two-step process. The first step is the production of a precursor Cu-In film by evaporating [10] or sputter deposition [11] in a vacuum system. In the second step, the precursor film is placed in a sulfurisation furnace filled with H 2 S gas or elemental sulfur vapour for the formation of a CIS film.…”