CuZnInSe₃‐based solar cells: Impact of copper concentration on vibrational and structural properties and device performance

Abstract

CuZnInSe3 (CZISe) is an interesting alternative for the acknowledged Cu(In,Ga)Se2 absorber layer in thin film solar cells. While the partial replacement of scarce and expensive indium and gallium by zinc decreases manufacturing costs, the solid solution between CuInSe2 and ZnSe opens interesting options for band gap tuning and grading. Its potential as an absorber layer in photovoltaic devices has been demonstrated by obtaining 7.4 and 7.6 % efficiency in CZISSe‐ and CZISe‐based devices, respectively. On the other hand, the inherent complexity of the quaternary CZISe together with a lack of fundamental insights puts a limit to its current development. We present insights on the influence of the copper content ([Cu]/([Zn] + [In]) ratio) on the structural and optoelectronic properties of CZISe as well as the formation of secondary phases. By means of XRD and Raman scattering analyses, in addition to the sphalerite CZISe structure, a chalcopyrite Cu‐In‐Zn‐Se phase was found for high copper concentrations. On the contrary, for low Cu concentrations, unambiguous indications of a new ordered vacancy compound (OVC)–like phase formation both in XRD patterns and in Raman spectra were found. Conditions of pre‐resonant Raman scattering were applied to emphasize the new found phase and to estimate its concentration. Finally, the influence of each phase on the optoelectronic parameters and performance of solar cells with efficiencies of up to 7.4 % was studied.

Multiwavelength excitation Raman scattering study of Sb 2 Se 3 compound: fundamental vibrational properties and secondary phases detection

“…Previously the high potential of the Raman spectroscopy for the complete solar cell characterization was established. 26,54,55 Indeed, clear methodologies for controlling the properties of different layers in thin film solar cells were shown. 51 However, a fine reference Raman spectrum should be measured before developing any methodologies.…”

Structural and vibrational properties of α- and π-SnS polymorphs for photovoltaic applications

“…Refs. [22][23][24]). In addition, Raman-based methodologies were proposed to analyse the critical parameters of other layers in a thin film solar cells, such as thickness of a buffer layer [25,26], and charge carrier concentrations in a top contact transparent conductive oxide (TCO) layer [27,28].…”

Stability of Cu2ZnSnSe4/CdS heterojunction based solar cells under soft post-deposition thermal treatments

“…This technique already showed an impressive potential to detect different structural, compositional and defect related variations in multinary compounds in general [42][43][44][45] and in kesterite type compounds in particular [25,[46][47][48]. Moreover, Raman spectroscopy is a fast and non-destructive technique, and by varying the excitation wavelength allows to analyze different layers in already completed devices [42,46].…”