Role of electron-phonon coupling and thermal expansion on band gaps, carrier mobility, and interfacial offsets in kesterite thin-film solar cells

Abstract

The efficiencies of solar cells based on kesterite Cu${}_2$ZnSnS${}_4$ (CZTS) and Cu${}_2$ZnSnSe${}_4$ (CZTSe) are limited by a low open-circuit voltage due to high rates of non-radiative electron-hole recombination. To probe the origin of this bottleneck, we calculate the band offset of CZTS(Se) with CdS, confirming a weak spike of 0.1 eV for CZTS/wurtzite-CdS and a strong spike of 0.4 eV for CZTSe/wurtzite-CdS. We also consider the effects of temperature on the band alignment, finding that increasing temperature significantly enhances the spike-type offset. We further resolve an outstanding discrepancy between measured and calculated phonon frequencies for the kesterites, and use these to estimate the upper limit of electron and hole mobilities based on optic phonon Fröhlich scattering, which uncovers an intrinsic asymmetry with faster (minority carrier) electron mobility.

arXiv comment5 pages, 3 figures, includes supplementary material

References in corpus (10)

• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Calculating polaron mobility in halide perovskites
• Lattice dynamics and electron-phonon coupling calculations using non-diagonal supercells
• Verification of first-principles codes: comparison of total energies, phonon frequencies, electron-phonon coupling and zero-point motion correction to the gap between ABINIT and QE/Yambo
• Comparing electron-phonon coupling strength in diamond, silicon and silicon carbide: First-principles study
• Ab initio thermodynamic model of Cu${}_2$ZnSnS${}_4$
• Giant electron-phonon interactions in molecular crystals and the importance of non-quadratic coupling
• First-principles investigation of the structural, dynamical and dielectric properties of kesterite, stannite and PMCA phases of Cu2ZnSnS4
• Opposing effects of stacking faults and antisite domain boundaries on the conduction band edge in kesterite quaternary semiconductors

Cited by in corpus (6)

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• Discovery of the Zintl-phosphide BaCd${}_2$P${}_2$ as a long carrier lifetime and stable solar absorber
• Assessing carrier mobility, dopability, and defect tolerance in the chalcogenide perovskite BaZrS${}_3$
• Finding a junction partner for candidate solar cell absorbers enargite and bournonite from electronic band and lattice matching
• Open-Circuit Voltage Deficit in Cu2ZnSnS4 Solar Cells by Interface Band Gap Narrowing
• Parallel Exploration of the Optoelectronic Properties of (Sb,Bi)(S,Se)(Br,I) Chalcohalides