Chelating-agent-assisted control of CsPbBr3 quantum well growth enables stable blue perovskite emitters

Abstract

Metal halide perovskites have emerged as promising candidates for solution-processed blue light-emitting diodes (LEDs). However, halide phase segregationand the resultant spectral shiftat LED operating voltages hinders their application. Here we report true-blue LEDs employing quasi-two-dimensional cesium lead bromide with a narrow size distribution of quantum wells, achieved through the incorporation of a chelating additive. Ultrafast transient absorption spectroscopy measurements reveal that the chelating agent helps to control the quantum well thickness distribution. Density functional theory calculations show that the chelating molecule destabilizes the lead species on the quantum well surface and that this in turn suppresses the growth of thicker quantum wells. Treatment with γ-aminobutyric acid passivates electronic traps and enables films to withstand 100°C for 24 h without changes to their emission spectrum. LEDs incorporating γ-aminobutyric acid-treated perovskites exhibit blue emission with Commission Internationale de l'Éclairage coordinates of (0.12, 0.14) at an external quantum efficiency of 6.3%.

Memory Seeds Enable High Structural Phase Purity in 2D Perovskite Films for High‐Efficiency Devices

“…Unfortunately, these efforts have had limited success, and do not generalize to all types of 2D perovskites. [30][31][32][33] Our previously reported hot casting method seems to yield better phase purity in thin films for a few types of 2D perovskites, yet there is little understanding of the intermediate chemical steps in the films formation, which has limited the dissemination of this method to other 2D perovskites. [34] We anticipate that the discovery of a reliable synthesis method to fabricate phase pure 2D perovskite thin films will enable optoelectronic devices that concomitantly exhibit high efficiency, scalability, long-term operational stability, as well as pave the path for new types of devices, which exploit the rich physics of 2D materials.…”

High-performance quasi-2D perovskite light-emitting diodes: from materials to devices

“…In addition to mixed-cation strategies, a judicious phase distribution can be achieved by rationally screening additives. Wang et al 122 incorporated a chelating agent, γ-aminobutyric acid (GABA), into a PEA 2 Cs n − 1 Pb n Br 3 n +1 film. Theoretical calculations indicated that the coordination tendency of small chelating molecules towards PbBr 2 in the vicinity of the perovskite could inhibit the binding of PbBr 2 to the perovskite surface, suppressing the growth of the large n phase.…”

“…7e, f ). The efficient energy transfer from the judicious phase distribution of the films can increase the PLQY and realize true-blue emission (EL at 478 nm) 122 . In conclusion, after a series of artificial designs and interventions regarding the phase distribution, the optical properties of pure red and blue quasi-2D perovskite films have significantly improved, paving the way for high-performance pure red and blue quasi-2D PeLED manufacture.…”

Using steric hindrance to manipulate and stabilize metal halide perovskites for optoelectronics

“…Wang et al found that γ-aminobutyric acid (3-ABA) which has a similar structure to 5-Ava can control the distribution of n values in the PEA 2 Cs n −1 Pb n Br 3 n +1 perovskite and suppress the formation of thicker quantum wells. 149 Bifunctional 3-ABA can also passivate trap states of perovskite films and achieve a high EQE of 6.3% for blue PeLEDs.…”