Formation of nanometer-sized Cu-Sn-Se particles in Cu2ZnSnSe4 thin-films and their effect on solar cell efficiency

Schwarz, Torsten; Cojocaru‐Mirédin, Oana; Mousel, Marina; Redinger, Alex; Raabe, Dierk; Choi, Pyuck‐Pa

doi:10.1016/j.actamat.2017.04.056

Cited by 3 publications

(2 citation statements)

References 40 publications

(60 reference statements)

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“…Consequently, all three binary phases are present in the layer and coexist within an area of only a few micrometers in size [119]. Nano-to micrometer-sized secondary phases, in particular ZnSe segregations, were also observed by TEM-EDX and atom probe tomography (APT) for CZTSe thin films with an overall Zn-rich composition formed by selenization of co-evaporated Cu-Zn-Sn-Se precursors [121,122] and for CZTSSe thin films prepared in a sequential solution-based process [123]. Secondary phase segregations are thus a common feature of nonstoichiometric kesterite thin films and may occur for a large range of integral layer compositions and growth techniques.…”

Section: Compositional Homogeneity On the Nano-to Micrometer Scalementioning

confidence: 95%

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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Section: Compositional Homogeneity On the Nano-to Micrometer Scalementioning

confidence: 95%

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

et al. 2019

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“…In principle, inhomogeneity of absorber main elements in CZTS is expected because the system exhibits strong tendencies of secondary phase formation due to the narrow compositional range of CZTS. [35] The high diffusivity of Cu in the compound is argued to facilitate the nucleation of Cu 2-x Se phases in CZTSe, [36,37] which are commonly observed at the absorber surface and near grain boundaries. [38] Investigations using in situ heating in a scanning electron transmission microscope have shown that this is influenced by migration of grain boundaries.…”

Section: Resultsmentioning

confidence: 99%

Dynamic Impurity Redistributions in Kesterite Absorbers

Grini

Aboulfadl

Ross

et al. 2020

Physica Status Solidi (b)

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Cu2ZnSn(S,Se)4 is a promising nontoxic earth‐abundant solar cell absorber. To optimize the thin films for solar cell device performance, postdeposition treatments at temperatures below the crystallization temperature are normally performed, which alter the surface and bulk properties. The polycrystalline thin films contain relatively high concentrations of impurities, such as sodium, oxygen and hydrogen. During the treatments, these impurities migrate and likely agglomerate at lattice defects or interfaces. Herein, impurity redistribution after air annealing for temperatures up to 200 °C and short heavy water treatments are studied. In addition, nonuniformities of the sodium distribution on a nanometer and micrometer scale are characterized by atom probe tomography and secondary ion mass spectrometry, respectively. Sodium and oxygen correlate to a greater extent after heat treatments, supporting strong binding between the two impurities. Redistributions of these impurities occur even at room temperature over longer time periods. Heavy water treatments confirm out‐diffusion of sodium with more incorporation of oxygen and hydrogen. It is observed that the increased hydrogen content does not originate from the heavy water. The existence of an “ice‐like” layer on top of the Cu2ZnSnS4 layer is proposed.

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Atomistic consideration of earth-abundant chalcogenide materials for photovoltaics: Kesterite and beyond

et al. 2018

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Formation of nanometer-sized Cu-Sn-Se particles in Cu2ZnSnSe4 thin-films and their effect on solar cell efficiency

Cited by 3 publications

References 40 publications

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

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

Dynamic Impurity Redistributions in Kesterite Absorbers

Atomistic consideration of earth-abundant chalcogenide materials for photovoltaics: Kesterite and beyond

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