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Compositionally induced valence-band offset at the grain boundary of polycrystalline chalcopyrites creates a hole barrier
Clas Persson,Alex Zunger +1 more
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In this paper, first-principles calculations of model grain boundaries (GBs) in CuInSe2 and CaGaSe2 show that cation-terminated GBs have a valence-band offset with respect to the grain interior (GI), thus depriving electrons there from recombination at the GB defects.Abstract:
First-principles calculations of model grain boundaries (GBs) in CuInSe2 and CaGaSe2 show that cation-terminated GBs have a valence-band offset with respect to the grain interior (GI). This offset repels holes from the GBs, thus depriving electrons there from recombination at the GB defects. Anion-terminated GBs have no such valence offset. CuGaSe2 has, in addition, a conduction-band offset at the GB/GI interface, attracting electrons to the GBs. These features explain how polycrystalline chalcopyrite solar cells could outperform their crystalline counterparts.read more
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Classification of lattice defects in the kesterite Cu2ZnSnS4 and Cu2ZnSnSe4 earth-abundant solar cell absorbers.
TL;DR: The calculated properties explain the experimental observation that Cu poor and Zn rich conditions result in the highest solar cell efficiency, as well as suggesting an efficiency limitation in Cu2ZnSn(S,Se)4 cells when the S composition is high.
Journal ArticleDOI
Assessment of correction methods for the band-gap problem and for finite-size effects in supercell defect calculations: Case studies for ZnO and GaAs
Stephan Lany,Alex Zunger +1 more
TL;DR: In this paper, the authors compared the results of different gap-correction methods and concluded that to date there is no universal scheme for band gap correction in general defect systems, and they turn instead to classification of different types of defect behavior to provide guidelines on how the physically correct situation in an LDA defect calculation can be recovered.
Journal ArticleDOI
Electronic and optical properties of Cu2ZnSnS4 and Cu2ZnSnSe4
TL;DR: In this paper, the electronic structure as well as the optical response of kesterite and stannite structures of Cu2ZnSnS4 and CoS4 were analyzed by a relativistic full-potential linearized augmented plane.
Journal ArticleDOI
Accurate prediction of defect properties in density functional supercell calculations
Stephan Lany,Alex Zunger +1 more
TL;DR: In this article, a scaling of the Madelung-like screened first-order correction term is proposed to correct the formation energy of charged defects in semiconductors, by potential alignment.
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Low band gap liquid-processed CZTSe solar cell with 10.1% efficiency
TL;DR: A low band gap liquid-processed Cu2ZnSn(Se1−xSx)4 (CZTSSe) solar cell with x ≈ 0.03 is prepared from earth abundant metals, yielding 10.1% power conversion efficiency as discussed by the authors.
References
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Efficient bulk heterojunction photovoltaic cells using small-molecular-weight organic thin films
TL;DR: This method results in a power conversion efficiency 50 per cent higher than the best values reported for comparable bilayer devices, suggesting that this strained annealing process could allow for the formation of low-cost and high-efficiency thin film organic solar cells based on vacuum-deposited small-molecular-weight organic materials.
Journal ArticleDOI
Anomalous Grain Boundary Physics in Polycrystalline CuInSe2: The Existence of a Hole Barrier
Clas Persson,Alex Zunger +1 more
TL;DR: First-principles modeling of grain boundaries (GB) in CuInSe2 semiconductors reveals that an energetic barrier exists for holes arriving from the grain interior (GI) to the GB, arising from reduced p-d repulsion due to Cu-vacancy surface reconstruction.
Journal ArticleDOI
Device and material characterization of Cu(InGa)Se2 solar cells with increasing band gap
TL;DR: In this article, thin-film solar cells have been fabricated from Cu(InGa)Se2 films which were deposited by four-source elemental evaporation with [Ga]/([In]+[Ga]) from 0.27 to 0.69 corresponding to a band gap from 1.16 to 1.45 eV.
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Anomalous Grain Boundary Physics in Polycrystalline CuInSe2: The Existence of a Hole Barrier
Clas Persson,Alex Zunger +1 more