Blue Perovskite Nanocrystal Light‐Emitting Devices via the Ligand Exchange with Adamantane Diamine

Takayuki Chiba*, Shota Ishikawa, Jun Sato, Yoshihito Takahashi, Hinako Ebe, Satoru Ohisa, Junji Kido*

https://onlinelibrary.wiley.com/doi/10.1002/adom.202000289

Abstract
Metal halide perovskite nanocrystals (NCs) have been established as promising materials for light‐emitting devices (LEDs) due to their interesting optoelectrical properties, including high photoluminescence quantum yield (PLQY) and high color purity with narrow full width at half maximum (FWHM). However, blue perovskite LEDs, with an emission wavelength below 470 nm, require further investigation to improve their performance. Here, it is demonstrated that mixed‐halide CsPb(Cl/Br)3 NCs prepared by ligand exchange with the rigid bidentate structure of adamantane‐1,3‐diamine (ADDA) can be used for blue LEDs. The ligand exchange of CsPb(Cl/Br)3 NCs with ADDA improves PLQY without changing the peak wavelength and FWHM. The LEDs based on ligand exchange NCs with ADDA show an external quantum efficiency (EQE) of 0.49%. Moreover, a quaternary ammonium salt, oleylammonium chloride (OAM‐Cl), is also investigated as an interfacial layer to reduce current density. The LED fabricated with OAM‐Cl reaches an EQE of 1.1% and luminance of 43.2 cd m−2 at the electroluminescence wavelength of 456 nm, representing significantly higher performance compared to that of LEDs without OAM‐Cl layers. Therefore, the ligand exchange of NCs with ADDA and the use of a passivation layer comprising OAM‐Cl facilitate an improvement in the LED performance.

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