Journal
ADVANCED FUNCTIONAL MATERIALS
Volume 30, Issue 17, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adfm.202000653
Keywords
coherent heterostructures; first-principles calculations; halide double-perovskites; photoluminescence; semiconductor alloys
Categories
Funding
- National Natural Science Foundation of China [61722402, 91833302]
- National Key Research and Development Program of China [2016YFB0700700]
- Shanghai Academic/Technology Research Leader [19XD1421300]
- Science Challenge Project [TZ2018004]
- Fok Ying Tung Education Foundation [161060]
- Fundamental Research Funds for the Central Universities
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Through first-principles calculations, it is found that two lattice-matched halide double-perovskites, Cs2NaBiBr6 and Cs2AgBiBr6, have a type-I band alignment and can form highly miscible alloys in which the disordering makes the bandgaps become direct and activates the direct transition from the valence to conduction band edge, leading to a strong optical absorption and high radiative recombination rate. The bandgaps of the alloys are tunable in a wide range of 1.93-3.24 eV, while the lattice constants remain unchanged. This advantage inspires the design of a coherent crystalline matrix based on Cs-2(Na,Ag)BiBr6 alloys, in which the Ag-rich and narrower-bandgap regions are embedded in the Na-rich and wide-bandgap region with lattice-matched and coherent interfaces. The type-I band alignment drives the photogenerated excitons into the narrower-bandgap Ag-rich regions, so the regions become light-emitting centers with a high photoluminescence quantum yield (PLQY). The bandgaps of the Ag-rich regions are tunable, so the color of emitted light can be adjusted, making a broadband emission possible. Such kind of coherent crystalline matrix with high-PLQY and broadband emission can also be fabricated based on the alloys of other lattice-matched halide double-perovskites, demonstrating the flexibility of band structure engineering in the coherent heterostructures of various halide double-perovskites.
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