Halide perovskite
nanocrystals (PNCs) exhibit growing attention
in optoelectronics due to their fascinating color purity and improved
intrinsic properties. However, structural defects emerging in PNCs
progressively hinder the radiative recombination and carrier transfer
dynamics, limiting the performance of light-emitting devices. In this
work, we explored the introduction of guanidinium (GA+)
during the synthesis of high-quality Cs1–xGAxPbI3PNCs as a promising
approach for the fabrication of efficient bright-red light-emitting
diodes (R-LEDs). The substitution of Cs by 10 mol % GA allows the
preparation of mixed-cation PNCs with PLQY up to 100% and long-term
stability for 180 days, stored under air atmosphere and refrigerated
condition (4 °C). Here, GA+cations fill/replace Cs+positions into the PNCs, compensating intrinsic defect sites
and suppressing the nonradiative recombination pathway. LEDs fabricated with this optimum material show an external quantum efficiency
(EQE) near to 19%, at an operational voltage of 5 V (50–100
cd/m2) and an operational half-time (t50) increased 67% respect CsPbI3R-LEDs. Our
findings show the possibility to compensate the deficiency through
A-site cation addition during the material synthesis, obtaining less
defective PNCs for efficient and stable optoelectronic devices.