Manipulating the Trade‐off Between Quantum Yield and Electrical Conductivity for High‐Brightness Quasi‐2D Perovskite Light‐Emitting Diodes

Abstract

Quasi-two-dimensional (quasi-2D) perovskites are attracting much attention due to their impressive luminescence properties. However, the introduction of insulating bulky cations reduces the charge transport property of mixeddimensional perovskites and leads to lowered brightness and increased turn-on voltage. The trade-off between high photoluminescence quantum yield (PLQY) and electrical conductivity should be well manipulated to obtain high-performance perovskite light-emitting diodes (PeLEDs). Herein, quasi-2D perovskite BA 2 (CsPbBr 3 ) n-1 PbBr 4 -PEO with high PLQY and excellent carrier injection efficiency is demonstrated by incorporating bulky n-butylammonium bromide (BABr), CsPbBr 3 , and polyethylene oxide (PEO). BA can intercalate into the three-dimensional perovskite framework to form a layered (quasi-2D) perovskite structure. The ion conductive polymer PEO is used to protect quasi-2D perovskite crystals. Additional BABr is removed by using anhydrous isopropyl alcohol as a washing agent due to its selective dissolubility. By carefully modulating the optical and electrical properties of quasi-2D perovskite films, the maximum luminance of PeLEDs is dramatically enhanced from 191 to 33533 cd m −2 , which is the brightest green quasi-2D PeLED reported thus far, leading to an increase in external quantum efficiency from 1.81% to 8.42%. This work provides a promising route to control the optical and electrical properties of quasi-2D perovskite films for high-performance optoelectronic devices.

Critical Role of Organic Spacers for Bright 2D Layered Perovskites Light‐Emitting Diodes

“…Our study suggests that the choice of organics is critical to obtain highly emissive 2D perovskites, where PEA cation included 2D hybrid perovskites show extended lifetime and large degree of localization that promote the radiative recombination. Interestingly, in Cs‐based 2D perovskites, the BA incorporated materials are more emissive 16,32. While the thin film crystalline quality for the PEABr and BABr thin films in our study are comparable evidenced by GIWAXS and SEM image analysis, the PEABr film contains more low n‐valued perovskite phase judging from the absorption and PL spectrum.…”

“…Motivated by the high emission quantum efficiency and large tunability in the optical properties, many efforts were devoted to the fabrication of light emitting diodes (LEDs) using quasi 2D/3D perovskites6–8 and low‐dimensional perovskites 9–14. The typical quasi 2D/3D and low‐dimensional perovskite based LEDs output high brightness of 10 3 –10 5 cd m −2 along with external quantum efficiency of 10–20% 9,12,15,16. The emission mechanisms underpinning such high performances, have been attributed to various physical origins.…”

Multifunctional p‐Type Carbon Quantum Dots: a Novel Hole Injection Layer for High‐Performance Perovskite Light‐Emitting Diodes with Significantly Enhanced Stability

“…The resulting perovskite thin film was characterized by XRD pattern as shown in Figure S3 (Supporting Information). The diffraction peaks at 15.1°, 21.3°, 30.3°, and 35.2° can be attributed to the (101), (121), (202), and (141) planes of orthorhombic CsPbBr 3 crystal ( Pnma ) . The broaden diffraction peaks confirmed the formation of small‐sized perovskite grains.…”

“…The incorporation of long‐chain alkyl organic cations leads to the formation of Ruddlesden–Popper perovskites with high photoluminescence (PL) quantum yield (PLQY). However, the complex phase distribution of low‐dimensional perovskite is expected to inhibit the transport of charge carriers due to their wider bandgaps . The addition of a small amount of 18‐crown‐6 can effectively suppress the crystallization of the organic phase and passivate the defects in perovskite crystals .…”

“…The absorption spectra of perovskite thin films were measured using a Shimadzu UV‐2450 spectrophotometer. The PLQY of the perovskite films was recorded through an absolute method according to previous reports …”