DESIGN OF QUATERNARY CHALCOGENIDE PHOTOVOLTAIC ABSORBERS THROUGH CATION MUTATION.
Presented at: 34th IEEE Photovoltaic Specialists Conference, Philadelphia, PA.
Design of chalcogenide photovoltaic absorbers is carried out systematically through sequential cation mutation, from binary to ternary to quaternary compounds, using first-principles electronic structure calculations. Several universal trends are identified for two classes of quaternary chalcogenides (I-2-II-IV-VI4 and I-III-II2-VI4 systems). For example, the lowest-energy structure always has larger lattice constant a, smaller tetragonal distortion parameter n = c/2a, and larger band gap than the metastable structures for common-row cation mutations. The band structure changes on mutation illustrate that although the band gap decreases from binary II-VI to ternary I-III-VI2 are mostly due to the p-d repulsion in the valence band, the decreases from ternary I-III-VI2 to quaternary I-2-II-IV-VI4 chalcogenides are due to the downshift in the conduction band caused by the wavefunction localization on the group IV cation site. We find that I-2-II-IV-VI4 compounds are more stable in the kesterite structure, whereas the widely-assumed stannite structure reported in the literature is most likely due to partial disorder in the I-II (001) layer of the kesterite phase. Ten compounds are predicted have band gaps close to the 1 to 2 eV energy window suitable for photovoltaics.
|Type:||Conference item (UNSPECIFIED)|
|Title:||DESIGN OF QUATERNARY CHALCOGENIDE PHOTOVOLTAIC ABSORBERS THROUGH CATION MUTATION|
|Event:||34th IEEE Photovoltaic Specialists Conference|
|Dates:||07 June 2009 - 12 June 2009|
|Keywords:||AUGMENTED-WAVE METHOD, BAND OFFSETS|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences
UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry
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