CZTS solar cell device simulations with varying absorber thickness

Frisk, Christopher; Ren, Yi; Li, Shuyi; Platzer‐Björkman, Charlotte

doi:10.1109/pvsc.2015.7355794

Cited by 6 publications

(6 citation statements)

References 9 publications

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“…This collection depth is compatible with short space charge region widths and minority carrier diffusion lengths reported previously in Se containing CZTS compound . Detailed device analysis and modeling of our samples will be reported separately .…”

Section: Discussionsupporting

confidence: 86%

Influence of the Cu₂ZnSnS₄ absorber thickness on thin film solar cells

Ren

Scragg

Frisk

et al. 2015

Physica Status Solidi (a)

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In this study, we investigate the influence of absorber thickness on Cu 2 ZnSnS 4 (CZTS) solar cells, ranging from 500 to 2000 nm, with nearly constant metallic composition. Despite the observed ZnS and SnS phases on the surface and backside of all absorber films, scanning electron microscopy, Raman scattering, and X-ray diffraction show no large variations in material quality for the different thicknesses. The open-circuit voltage (V oc ), short-circuit current and overall power conversion efficiency of the fabricated devices show an initial improvement as the absorber thickness increases but saturate when the thickness exceeds 750 nm. External quantum efficiency (EQE) measurements suggest that the current is mainly limited by collection losses. This can result from nonoptimal bulk quality of the CZTS absorber (including the presence of secondary phases), which is apparently further reduced for the thinnest devices. The observed saturation of V oc agrees with the expected influence from strong interface recombination. Finally, an effective collection depth of 750-1000 nm for the minority carriers generated in the absorber can be estimated from EQE, indicating that the proper absorber thickness for our device process is approximately 1000 nm. Performance could be improved for thicker films, if the collection depth can be increased.

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Section: Discussionsupporting

confidence: 86%

Influence of the Cu₂ZnSnS₄ absorber thickness on thin film solar cells

Ren

Scragg

Frisk

et al. 2015

Physica Status Solidi (a)

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“…This difference could be related to the formation of secondary phases at the front and rear of ultrathin CZTS absorbers, an issue not present in the CIGSe solar cells, or to the shorter diffusion length of CZTS absorbers. Indeed, the passivation layer with nanosized point openings is effective in reducing the impact of ZnS and SnS secondary phase segregation but primarily at the rear CZTS interface, and the electron diffusion length is anticipated to be between 250 and 500 nm only (from the simulations performed in [15]- [17]). Note that-possibly-these EQE curves may even provide an opportunity to distinguish between bulk and rear interface improvement of the rear passivation layer in ultrathin CZTS solar cells.…”

Section: Analysis Of the Rear Passivated Czts Solar Cell Results Cmentioning

confidence: 99%

“…These secondary phases can be detrimental to the device performance, since the SnS phase has a lower bandgap than CZTS phase and could modify the interface properties, while the ZnS phase can block current flow and introduce dead areas [16]. Indeed, using the Solar Cell Capacitance Simulator software, in-depth simulations have been performed and compared with these empirical data, indicating that the lower performance of the ultrathin CZTS solar cells is caused by both a reduced bulk quality and high rear interface recombination [17].…”

Section: A Czts Solar Cells With Ultrathin Absorber Layer As Charactmentioning

confidence: 99%

Rear Surface Optimization of CZTS Solar Cells by Use of a Passivation Layer With Nanosized Point Openings

Vermang

Ren

Donzel‐Gargand

et al. 2016

IEEE J. Photovoltaics

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Previously, an innovative way to reduce rear interface recombination in Cu(In,Ga)(S,Se) 2 (CIGSSe) solar cells has been successfully developed. In this work, this concept is established in Cu 2 (Zn,Sn)(S,Se) 4 (CZTSSe) cells to demonstrate its potential for other thin-film technologies. Therefore, ultrathin CZTS cells with an Al 2 O 3 rear surface passivation layer having nanosized point openings are fabricated. The results indicate that introducing such a passivation layer can have a positive impact on open-circuit voltage (V O C ; +17%rel.), short-circuit current (J S C ; +5%rel.), and fill factor (FF; +9%rel.), compared with corresponding unpassivated cells. Hence, a promising efficiency improvement of 32%rel. is obtained for the rear passivated cells.

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“…In connection to the previously published thickness series, device modelling in SCAPS was performed. 22 A model for the thick, reference device was established based on optical data from ellipsometry 23 and device characterisation. 24 The experimental results from the thickness series were partly reproduced in modelling, but the drastic drop in performance for thinnest absorbers was not seen.…”

Section: Resultsmentioning

confidence: 99%