Ca2+-doping for stable pure red CsPbI3 quantum dot light-emitting diodes

Abstract

α-CsPbI₃ quantum dots (QDs) are ideal materials for pure red light-emitting diodes (LEDs) to achieve a wide color gamut display. Small α-CsPbI₃ QDs have a large specific surface area and exhibit a near-spherical shape, discontinuous crystal faces with intense surface defects and crystal distortion, which accelerates phase transition and optoelectronic degradation. Additionally, the tolerance factor for α-CsPbI₃ is too small to be stabilized. Herein, we report a Ca²⁺ doping strategy to tune the CsPbI₃ tolerance factor to inhibit its phase transition, enhance its structural stability, decrease the lattice distortion and reduce the defects. The stability of the Ca²⁺-doped CsPbI₃ QDs under harsh conditions are improved. The Commission Internationale de l’Eclairage coordinates of the perovskite LEDs are (0.706, 0.294), satisfying wide color gamut as well as Rec. 2020 requirements for pure red, and the LEDs exhibit a 1.67-fold enhancement in half-lifetime to 32.0 min at a voltage of 5.0 V (346 cd m⁻²) and 1.31-fold enhancement in the EQE to 10.3%.