Structural and photoelectron spectroscopic studies of band alignment at the Cu2ZnSnS4/CdS heterojunction with slight Ni doping in Cu2ZnSnS4

Chen, Hui Ju; Fu, Sheng Wen; Wu, Shih Hsiung; Tsai, Tsung Chieh; Wu, Hsuan Ta; Shih, Chuan Feng

doi:10.1088/0022-3727/49/33/335102

Cited by 16 publications

(16 citation statements)

References 60 publications

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“…It is apparent CdS forms a large cliff-like CBO (Type II) at the heterojunction with CZTSSe whereas In 2 S 3 forms a modest spike-like CBO (Type I). The larger CBO relative to previous reports 22,25,39,40 can arise due to the error introduced by the low-resolution IPES measurements.…”

Section: A Band Alignment At Buffer/cztsse Interfacecontrasting

confidence: 58%

Defect limitations in Cu2ZnSn(S, Se)4 solar cells utilizing an In2S3 buffer layer

Campbell

Gibbon

et al. 2020

Journal of Applied Physics

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Alternative n-type buffer layer such as In 2 S 3 have been proposed as Cd-free alternative in kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells. In this study, optical and electronic characterisation techniques together with device analysis and simulation were used to assess nanoparticle-based CZTSSe absorbers and solar cells with CdS and In 2 S 3 buffers. Photoluminescence spectroscopy indicated CZTSSe absorbers with In 2 S 3 buffer had a lower density of detrimental non-radiative defects and a higher concentration of copper vacancies V Cu + , responsible for p-type conductivity in CZTSSe, in comparison to the absorber with CdS buffer. Capacitance-voltage (C-V) measurements revealed the In 2 S 3 buffer-based CZTSSe devices had a three times higher apparent doping density and a consequently narrower space charge region than devices with a CdS layer. This resulted in poorer collection of photo-generated charge carriers in the near-IR region despite a more favourable band alignment as determined by X-ray photoelectron and inverse photoelectron spectroscopy. The presence of interfacial defect states in In 2 S 3 devices as determined by C-V and biased quantum efficiency measurements are also responsible for the loss in open-circuit voltage compared with reference devices with CdS.

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Section: A Band Alignment At Buffer/cztsse Interfacecontrasting

confidence: 58%

Defect limitations in Cu2ZnSn(S, Se)4 solar cells utilizing an In2S3 buffer layer

Campbell

Gibbon

et al. 2020

Journal of Applied Physics

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“…The negative conduction offsets reveal a cliff-like band alignment at both heterointerfaces. According to device simulations, the cliff can act as a barrier against injected electrons at forward bias, resulting in recombination of majority carriers via defects at the interface 14 , 15 , 27 , 41 . Neverthenless, with decreasing the absolute value of the conduction band offset in the case of CdS/ACZTS, the barrier is lowered, and this can ultimately result in an increase in Voc and FF in ACZTS devices.…”

Section: Discussionmentioning

confidence: 99%

Energy band alignment at the heterointerface between CdS and Ag-alloyed CZTS

Gansukh

Rodriguez

et al. 2020

Sci Rep

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Energy band alignment at the heterointerface between CdS and kesterite Cu2ZnSnS4 (CZTS) and its alloys plays a crucial role in determining the efficiency of the solar cells. Whereas Ag alloying of CZTS has been shown to reduce anti-site defects in the bulk and thus rise the efficiency, the electronic properties at the interface with the CdS buffer layer have not been extensively investigated. In this work, we present a detailed study on the band alignment between n-CdS and p-CZTS upon Ag alloying by depth-profiling ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). Our findings indicate that core-level peaks and the valence band edge of CdS exhibit a significant shift to a lower energy (larger than 0.4 eV) upon the etching of the CdS layer, which can be assigned due to band bending and chemical shift induced by a change in the chemical composition across the interface. Using a simplified model based on charge depletion layer conservation, a significantly larger total charge region depletion width was determined in Ag-alloyed CZTS as compared to its undoped counterpart. Our findings reveal a cliff-like band alignment at both CdS/CZTS and CdS/Ag-CZTS heterointerfaces. However, the conduction-band offset decreases by more than 0.1 eV upon Ag alloying of CZTS. The approach demonstrated here enables nanometer-scale depth profiling of the electronic structure of the p–n junction and can be universally applied to study entirely new platforms of oxide/chalcogenide heterostructures for next-generation optoelectronic devices.

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“…There can be different reasons why E A can be lower than the absorber's band gap when interface recombination is dominant [9]. Among them, a cliff-like conduction band offset (CBO) between CZTS and its typical heterojunction partner CdS (buffer layer) is often invoked because a large fraction of the existing CBO measurements [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] and calculations [21,[27][28][29][30][31][32][33] confirms it. Here, by "clifflike" or "negative" CBO we intend a lower-lying conduction band maximum of CdS with respect to CZTS(e) at the heterointerface, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

What is the band alignment of Cu 2 ZnSn(S,Se) 4 solar cells?

Crovetto

Hansen

2017

Solar Energy Materials and Solar Cells

141

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Structural and photoelectron spectroscopic studies of band alignment at the Cu₂ZnSnS₄/CdS heterojunction with slight Ni doping in Cu₂ZnSnS₄

Cited by 16 publications

References 60 publications

Defect limitations in Cu2ZnSn(S, Se)4 solar cells utilizing an In2S3 buffer layer

Defect limitations in Cu2ZnSn(S, Se)4 solar cells utilizing an In2S3 buffer layer

Energy band alignment at the heterointerface between CdS and Ag-alloyed CZTS

What is the band alignment of Cu 2 ZnSn(S,Se) 4 solar cells?

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