Optical properties and surface characterization of pulsed laser-deposited Cu 2 ZnSnS 4 by spectroscopic ellipsometry

Crovetto, Andrea; Cazzaniga, Andrea Carlo; Ettlinger, Rebecca Bolt; Schou, Jørgen; Hansen, Ole

doi:10.1016/j.tsf.2014.11.075

Cited by 21 publications

(16 citation statements)

References 10 publications

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“…In order to decrease the number of fitting parameters, we extracted the dielectric function of each layer independently in a separate ellipsometry measurement, as explained in the following sections. A Kramers-Kronig-consistent b-spline model was used to model the shape of the dielectric functions, as demonstrated previously [14]. This means that the imaginary part ε 2 (E) was fitted by a b-spline function using control points spaced by 0.2 eV, whereas the real part ε 1 (E) was not fitted independently but was instead derived by Kramers-Kronig integration.…”

Section: Methodsmentioning

confidence: 99%

Dielectric function and double absorption onset of monoclinic Cu 2 SnS 3 : Origin of experimental features explained by first-principles calculations

Crovetto

Chen

Ettlinger

et al. 2016

Solar Energy Materials and Solar Cells

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Section: Methodsmentioning

confidence: 99%

Dielectric function and double absorption onset of monoclinic Cu 2 SnS 3 : Origin of experimental features explained by first-principles calculations

Crovetto

Chen

Ettlinger

et al. 2016

Solar Energy Materials and Solar Cells

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“…[161,162] and Cu 2 ZnSn(S, Se) 4 [163] have been characterized by means of SE, in either single crystal, polycrystalline, or thin film forms, from the imaginary part of the dielectric constant. It is interesting to note here that significant efforts are being focused on the analysis of thin films through the modeling of surface roughness, secondary phases, and intermediate layers, with SE emerging as a potential characterization technique for the confirmation of their presence in the growth process [158,163,167,168]. The experimentally obtained energy values are presented in table 5.…”

Section: Se and Band Structure Calculations In Kesteritesmentioning

confidence: 99%

“…Theoretically calculated and experimentally obtained by SE energy transition values for Cu 2 Zn(Ge,Sn)(S,Se) 4 compounds (superscripts correspond to cited references). Tetragonal structure corresponding to stannite after the authors.Complementarily, the energy interband transitions in Cu 2 ZnSnS 4[100,155,158,[166][167][168], Cu 2 ZnSnSe 4[100,155], Cu 2 ZnGeS 4[159] and Cu 2 ZnGeSe 4[160] compounds, as well as their intermediate pseudoquaternary ones, Cu 2 Zn(Ge, Sn)S 4…”

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confidence: 99%

Point defects, compositional fluctuations, and secondary phases in non-stoichiometric kesterites

et al. 2019

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The efficiency of kesterite-based solar cells is limited by various non-ideal recombination paths, amongst others by a high density of defect states and by the presence of binary or ternary secondary phases within the absorber layer. Pronounced compositional variations and secondary phase segregation are indeed typical features of non-stoichiometric kesterite materials. Certainly kesterite-based thin film solar cells with an offstoichiometric absorber layer composition, especially Cu-poor/Zn-rich, achieved the highest efficiencies, but deviations from the stoichiometric composition lead to the formation of intrinsic point defects (vacancies, anti-sites, and interstitials) in the kesterite-type material. In addition, a non-stoichiometric composition is usually associated with the formation of an undesirable side phase (secondary phases). Thus the correlation between off-stoichiometry and intrinsic point defects as well as the identification and quantification of secondary phases and compositional fluctuations in non-stoichiometric kesterite materials is of great importance for the understanding and rational design of solar cell devices. This paper summarizes the latest achievements in the investigation of identification and quantification of intrinsic point defects, compositional fluctuations, and secondary phases in non-stoichiometric kesterite-type materials.This work focuses on structural variations in kesterite-type compound semiconductors, in particular Cu/Zn disorder and intrinsic point defects, as well as on compositional variations, in particular stoichiometry deviations in the kesterite-type phase and the segregation of related binary and ternary phases.This review provides the vital approaches by discussing results and trends concerning intrinsic point defects and structural disorder, compositional fluctuations, and secondary phases on a macroscopic and microscopic scale and even on the nano-scale. Various analytical methods have been used in these studies.The review comprises five parts:A. Crystal structure, structural disorder, and intrinsic point defects in kesterites B. Raman spectroscopy investigations on kesterites OPEN ACCESS RECEIVED

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“…Si-based heterojunction intrinsic thin layer (HIT), CdTe, Cu(In,Ga)Se 2 (CIGS), and metal halide perovskite solar cells have all reached efficiencies above 20% [1] and can be manufactured at a relatively low cost. The earthabundant and non-toxic absorber Cu 2 ZnSn(S,Se) 4 (CZTS) has also been investigated extensively and has reached a promising 12.6% record efficiency [1].…”

Section: Introductionmentioning

confidence: 99%

“…The second important spectral region corresponds to the solar spectrum (optical frequencies). In this region, the relative permittivity becomes a complex number and describes the optical phenomena of light absorption and refraction in the solar cell material [4,5]. Optical optimization of solar cells has already received much attention in solar cell research and will not be treated here.…”

Section: Introductionmentioning

confidence: 99%

How the relative permittivity of solar cell materials influences solar cell performance

2017

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The relative permittivity of the materials constituting heterojunction solar cells is usually not considered as a design parameter when searching for novel combinations of heterojunction materials. In this work, we investigate whether such an approach is valid. Specifically, we show the effect of the materials permittivity on the physics and performance of the solar cell by means of numerical simulation supported by analytical relations. We demonstrate that, depending on the specific solar cell configuration and materials properties, there are scenarios where the relative permittivity has a major influence on the achievable conversion efficiency, and scenarios where its influence can be safely ignored. In particular, we argue that high-permittivity materials should always be the preferred choice as heterojunction partners of the absorber layer when prototyping new materials combinations. When the heterojunction partner has a high permittivity, solar cells are consistently more robust against several non-idealities that are especially likely to occur in early-stage development, when the device is not yet optimized.

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Optical properties and surface characterization of pulsed laser-deposited Cu 2 ZnSnS 4 by spectroscopic ellipsometry

Cited by 21 publications

References 10 publications

Dielectric function and double absorption onset of monoclinic Cu 2 SnS 3 : Origin of experimental features explained by first-principles calculations

Dielectric function and double absorption onset of monoclinic Cu 2 SnS 3 : Origin of experimental features explained by first-principles calculations

Point defects, compositional fluctuations, and secondary phases in non-stoichiometric kesterites

How the relative permittivity of solar cell materials influences solar cell performance

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