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Title: Nanocrystalline Cu{sub 2}ZnSnSe{sub 4} thin films for solar cells application: Microdiffraction and structural characterization

Abstract

This work presents a study of the structural characterization of Cu{sub 2}ZnSnSe{sub 4} (CZTSe) thin films by X-ray diffraction (XRD) and microdiffraction measurements. Samples were deposited varying both mass (M{sub X}) and substrate temperature (T{sub S}) at which the Cu and ZnSe composites were evaporated. CZTSe samples were deposited by co-evaporation method in three stages. From XRD measurements, it was possible to establish, with increased Ts, the presence of binary phases associated with the quaternary composite during the material's growth process. A stannite-type structure in Cu{sub 2}ZnSnSe{sub 4} thin films and sizes of the crystallites varying between 30 and 40 nm were obtained. X-ray microdiffraction was used to investigate interface orientations and strain distributions when deposition parameters were varied. It was found that around the main peak, 2ϴ = 27.1°, the Cu{sub 1.8}Se and ZnSe binary phases predominate, which are formed during the subsequent material selenization stage. A Raman spectroscopy study revealed Raman shifts associated with the binary composites observed via XRD.

Authors:
;  [1]
  1. Departmento de Física, Grupo de Materiales Nanoestructurados y sus Aplicaciones, Universidad Nacional de Colombia, Bogotá 11001 (Colombia)
Publication Date:
OSTI Identifier:
22597834
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 120; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COPPER SELENIDES; CRYSTALS; DEPOSITION; DEPOSITS; DISTRIBUTION; EVAPORATION; INTERFACES; NANOSTRUCTURES; PEAKS; RAMAN SPECTROSCOPY; SOLAR CELLS; STRAINS; SUBSTRATES; THIN FILMS; TIN SELENIDES; X RADIATION; X-RAY DIFFRACTION; ZINC SELENIDES

Citation Formats

Quiroz, Heiddy P., E-mail: hpquirozg@unal.edu.co, and Dussan, A., E-mail: adussanc@unal.edu.co. Nanocrystalline Cu{sub 2}ZnSnSe{sub 4} thin films for solar cells application: Microdiffraction and structural characterization. United States: N. p., 2016. Web. doi:10.1063/1.4958941.
Quiroz, Heiddy P., E-mail: hpquirozg@unal.edu.co, & Dussan, A., E-mail: adussanc@unal.edu.co. Nanocrystalline Cu{sub 2}ZnSnSe{sub 4} thin films for solar cells application: Microdiffraction and structural characterization. United States. doi:10.1063/1.4958941.
Quiroz, Heiddy P., E-mail: hpquirozg@unal.edu.co, and Dussan, A., E-mail: adussanc@unal.edu.co. Sun . "Nanocrystalline Cu{sub 2}ZnSnSe{sub 4} thin films for solar cells application: Microdiffraction and structural characterization". United States. doi:10.1063/1.4958941.
@article{osti_22597834,
title = {Nanocrystalline Cu{sub 2}ZnSnSe{sub 4} thin films for solar cells application: Microdiffraction and structural characterization},
author = {Quiroz, Heiddy P., E-mail: hpquirozg@unal.edu.co and Dussan, A., E-mail: adussanc@unal.edu.co},
abstractNote = {This work presents a study of the structural characterization of Cu{sub 2}ZnSnSe{sub 4} (CZTSe) thin films by X-ray diffraction (XRD) and microdiffraction measurements. Samples were deposited varying both mass (M{sub X}) and substrate temperature (T{sub S}) at which the Cu and ZnSe composites were evaporated. CZTSe samples were deposited by co-evaporation method in three stages. From XRD measurements, it was possible to establish, with increased Ts, the presence of binary phases associated with the quaternary composite during the material's growth process. A stannite-type structure in Cu{sub 2}ZnSnSe{sub 4} thin films and sizes of the crystallites varying between 30 and 40 nm were obtained. X-ray microdiffraction was used to investigate interface orientations and strain distributions when deposition parameters were varied. It was found that around the main peak, 2ϴ = 27.1°, the Cu{sub 1.8}Se and ZnSe binary phases predominate, which are formed during the subsequent material selenization stage. A Raman spectroscopy study revealed Raman shifts associated with the binary composites observed via XRD.},
doi = {10.1063/1.4958941},
journal = {Journal of Applied Physics},
number = 5,
volume = 120,
place = {United States},
year = {Sun Aug 07 00:00:00 EDT 2016},
month = {Sun Aug 07 00:00:00 EDT 2016}
}
  • Cu{sub 2}ZnSnSe{sub 4} thin-films for photovoltaic applications are investigated using combined atom probe tomography and ab initio density functional theory. The atom probe studies reveal nano-sized grains of Cu{sub 2}Zn{sub 5}SnSe{sub 8} and Cu{sub 2}Zn{sub 6}SnSe{sub 9} composition, which cannot be assigned to any known phase reported in the literature. Both phases are considered to be metastable, as density functional theory calculations yield positive energy differences with respect to the decomposition into Cu{sub 2}ZnSnSe{sub 4} and ZnSe. Among the conceivable crystal structures for both phases, a distorted zinc-blende structure shows the lowest energy, which is a few tens of meVmore » below the energy of a wurtzite structure. A band gap of 1.1 eV is calculated for both the Cu{sub 2}Zn{sub 5}SnSe{sub 8} and Cu{sub 2}Zn{sub 6}SnSe{sub 9} phases. Possible effects of these phases on solar cell performance are discussed.« less
  • Attempts to identify intermediates in a solution route to thin films of the high-temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 7} have led to the isolation of the mixed-metal cluster Ba{sub 2}Cu{sub 2}(OR){sub 4}(acac){sub 4}{center dot}2HOR (R = CH{sub 2}CH{sub 2}OCH{sub 3}) (1). This compound, which is the first example of a molecular barium-copper cluster, was isolated from the reaction of the copper dimer ((acac)Cu(OCH{sub 2}CH{sub 2}OCH{sub 3})){sub 2} with barium 2-methoxyethoxide, the first stage in the preparation of the thin-film precursor solution. Crystallographic data for 1 are as follows: formula = Ba{sub 2}Cu{sub 2}O{sub 20}C{sub 38}H{sub 72}, FW = 1250.5 g/mol,more » D{sub x} = 1.57 g/cm{sup 3}, space group = P{bar 1}, a = 10.797 (3) {angstrom}, b = 11.269 (1) {angstrom}, c = 12.109 (1) {angstrom}, {alpha} = 106.18 (1){degree}, {beta} = 100.93 (2){degree}, {gamma} = 102.98 (2){degree}, Z = 1, R = 0.031 for 4059 reflections with I {ge} 2{sigma}(I) and 2{theta}{le}50{degree}. Thin films prepared from this route showed superconducting transition temperatures of 85 K, only small amounts of impurity phases by X-ray powder diffraction, and {le} 0.1 atom % carbon as determined by nuclear reaction analysis.« less
  • Here, we determined the electrical junction (EJ) locations in Cu(In,Ga)Se 2 (CIGS) and Cu 2ZnSnSe 4 (CZTS) solar cells with ~20-nm accuracy by developing scanning capacitance spectroscopy (SCS) applicable to the thin-film devices. Cross-sectional sample preparation for the SCS measurement was developed by high-energy ion milling at room temperature for polishing the cross section to make it flat, followed by low-energy ion milling at liquid nitrogen temperature for removing the damaged layer and subsequent annealing for growing a native oxide layer. The SCS shows distinct p-type, transitional, and n-type spectra across the devices, and the spectral features change rapidly withmore » location in the depletion region, which results in determining the EJ with ~20-nm resolution. We found an n-type CIGS in the region next to the CIGS/CdS interface; thus, the cell is a homojunction. The EJ is ~40 nm from the interface on the CIGS side. In contrast, such an n-type CZTS was not found in the CZTS/CdS cells. The EJ is ~20 nm from the CZTS/CdS interface, which is consistent with asymmetrical carrier concentrations of the p-CZTS and n-CdS in a heterojunction cell. Our results of unambiguously determination of the junction locations contribute significantly to understanding the large open-circuit voltage difference between CIGS and CZTS.« less
  • Our contribution describes the influence of low-temperature annealing with and without applied voltage bias on thin-film Cu 2ZnSnSe 4 (CZTSe), Cu(In,Ga)Se 2 (CIGS), and CdS material properties and solar cell performance. In order to quantify the effects of cation disorder on CZTSe device performance, completed devices were annealed under open-circuit conditions at various temperatures from 110 degrees C to 215 degrees C and subsequently quenched. Measurements on these devices document systematic, reversible changes in solar-cell performance consistent with a reduction in CZTSe band tails at lower annealing temperatures. CIGS and CZTSe solar cells were also annealed at various temperatures (200more » degrees C for CIGS and 110 degrees C-215 degrees C for CZTSe) and subsequently quenched with continuously applied voltage bias to explore the effects of non-equilibrium annealing conditions. For both absorbers, large reversible changes in device characteristics correlated with the magnitude and sign of the applied voltage bias were observed. For CZTSe devices, the voltage-bias annealing (VBA) produced reversible changes in open-circuit voltage (VOC) from 289 meV to 446 meV. For CIGS solar cells, even larger changes were observed in device performance: photovoltaic (PV) conversion efficiency of the CIGS device varied from below 3% to above 15%, with corresponding changes in CIGS hole density of about three orders of magnitude. Findings from these VBA experiments are interpreted in terms of changes to the metastable point-defect populations that control key properties in the absorber layers, and in the CdS buffer layer. Computational device modeling was performed to assess the impacts of cation disorder on the CZTSe VOC deficit, and to elucidate the effects of VBA treatments on metastable point defect populations in CZTSe, CIGS, and CdS. Our results indicate that band tails impose important limitations on CZTSe device performance. Device modeling results also indicate that non-equilibrium processing conditions including the effects of voltage bias can dramatically alter point-defect-mediated opto-electronic properties of semiconductors. Implications for optimization of PV materials and connections to long-term stability of PV devices are discussed.« less