Efficient and High-Color-Purity Light-Emitting Diodes Based on In Situ Grown Films of CsPbX₃ (X = Br, I) Nanoplates with Controlled Thicknesses

Abstract

We report a facile solution-based approach to the in situ growth of perovskite films consisting of monolayers of CsPbBr nanoplates passivated by bulky phenylbutylammonium (PBA) cations, that is, two-dimensional layered PBA(CsPbBr)PbBr perovskites. Optimizing film formation processes leads to layered perovskites with controlled n values in the range of 12-16. The layered perovskite emitters show quantum-confined band gap energies with a narrow distribution, suggesting the formation of thickness-controlled quantum-well (TCQW) structures. The TCQW CsPbBr films exhibit smooth surface features, narrow emission line widths, low trap densities, and high room-temperature photoluminance quantum yields, resulting in high-color-purity green light-emitting diodes (LEDs) with remarkably high external quantum efficiencies (EQEs) of up to 10.4%. The solution-based approach is extended to the preparation of TCQW CsPbI films for high-color-purity red perovskite LEDs with high EQEs of up to 7.3%.

Emergence of Nanoplatelet Light-Emitting Diodes

“…Similar to MAPbBr 3 , 2D FAPbBr 3 NPLs can be very efficient emitters. Recently, with about 7–10 unit cells colloidal FAPbBr 3 NPLs, Kumar et al have reported a pure green LED [128]. The exciton-binding energy as high as 162 meV for 2D FAPbBr 3 perovskites via the dielectric quantum well engineering.…”

Lead halide perovskites: Recombining faster, emitting brighter

“…External quantum efficiency >10% [10,11] and ultrahigh brightness up to 5.9×10 5 cd m −2 [12] have been reported. The work of Becker et al reinforces the idea that lead halide perovskites are excellent light emitters.…”

In Situ Fabricated Perovskite Nanocrystals: A Revolution in Optical Materials

“…As mentioned above, the quasi 2D PNC structure can be denoted as L 2 A n−1 B n X 3n+1 . Plenty of investigations have been conducted on the choices of bulky cation L, including PEA, [56,63,64,[89][90][91][92] BA, [55,88,[93][94][95] ethylammonium (EA), [96] phenylmethylamine (PMA), [97] phenylbutylammonium (PBA), [98,99] naphthylmethylamine (NMA) [65,100] and 2-Phenoxyethylamine (POEA). [101] Similar to the pure 2D structure, with the space dimension reduced to nanosized 3D or quasi 2D, the PNCs exhibit strong excitonic behavior.…”

“…Nevertheless, it seems in some works that large OA cations can solely assist the in situ fabrication of PNCs without the participation of antisolvent. [65,98] Therefore, in contrast to the great success of film optimization, the understanding into the role of OA cations as well as antisolvents in the crystalline kinetics falls behind and needs to be clarified.…”

“…[55] Furthermore, by inserting the large OA molecules into the 3D perovskite structure, the resulted RP phase PNCs demonstrated PeLEDs with dramatically improved CE and EQE due to the energy funneling effect. [63][64][65]98,100] Very recently, a high efficient green emission PeLED employing quasi 2D PNCs was reported with record CE of 62.4 cd A −1 and EQE of 14.36%. [92] Through lowmagnification high-angle annular dark-field, an ordered spatial distribution of the RP phases where the majority of large-n phases are located close to the hole transporting layer is discovered by Wang and co-workers.…”