Role of Quantum Confinement in 10 nm Scale Perovskite Optoelectronics.

Quantum confinement-driven band structure engineering of metal halide perovskites (MHPs) is examined for realistically sized structures that consist of up to 105 atoms. The structural and compositional effects on band gap energies are simulated for crystalline CH3NH3PbX3 (X = I/Br/Cl) with a tight-binding approach that has been well-established for electronic structure calculations of multimillion atomic systems. Solid maps of band gap energies achievable with quantum dots, nanowires, and nanoplatelets concerning sizes, shapes, and halide compositions are presented, which should be informative to experimentalists for band gap designs. The pathway to suppress band gap instability that appeared in mixed halide perovskites is proposed, revealing that the red shift induced by halide phase separation can be hugely diminished by reducing sizes and adopting halides of lower electronegativity. Our modeling results on finite MHP structures of over 10 nm dimensions show a blueprint for designs of stable light-emitting sources with precisely controlled wavelengths.