Charge carrier confinement in nanocrystals is an effective route to enhance luminescence efficiency of metal halide perovskites. However, difficulty in handling surface ligands of colloidal perovskite nanocrystals and the defective surface of the processed nanocrystals limit radiative efficiency and the stability of nanocrystalline films. We report a novel approach to fabricate highly luminescent nanocrystalline polymorphic formamidinium lead tri-iodide (FAPbI3) films. The cubic perovskite nanocrystals are formed in situ by kinetic controlled solid-state phase conversion of a hexagonal polymorph. The perovskite nanocrystal surface is benign owing to the remnant polymorph forming a type I heterojunction with the nanocrystal surface, facilitating accelerated radiative recombination with suppressed trapping in the nanocrystals to which ultrafast carrier funneling occurs. This polymorphic energy funnel renders photoluminescence intensity enhanced by a factor of 58 compared to that of conventional bulk-FAPbI3 film. A proof-of-concept light-emitting diode device exhibited superior efficiency and stability in comparison to devices based on the conventional bulk-FAPbI3 film.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MIST) under contract numbers NRF-2020R1F1A1067223, 2012M3A6A7054861 (Global Frontier R&D Program on Center for Multiscale Energy System), 2016M3D1A1027663, and 2016M3D1A1027664 (Future Materials Discovery Program) and by the Material and Component Industrial Future Growth Engine Program (20006476) funded by the Ministry of Trade, Industry & Energy (MOTIE).
All Science Journal Classification (ASJC) codes
- Chemistry (miscellaneous)
- Renewable Energy, Sustainability and the Environment
- Fuel Technology
- Energy Engineering and Power Technology
- Materials Chemistry