Efficient NIR Perovskite Light-Emitting Diodes Enabled by Incorporating an Anthracene Derivative as a Bifunctional Electron Transport Layer

Abstract

Exploring multifunctional charge transport materials with well-matched energy-levels alignment and compatible interfaces is deemed a potential approach toward high-performance perovskite light-emitting diodes (PeLEDs). Herein, an anthracene derivative, 1-[4-(10-[1,1′biphenyl]-4-yl-9-anthracenyl)phenyl]-2-ethyl-1H-benzimidazole (BAEBi), is demonstrated as an efficient electron tranport layer (ETL) as well as an effective surface passivation agent for near-infrared (NIR) quasi twodimensional (Q-2D) PeLEDs. Owing to the promising electron injection and transport capability of BAEBi, an improved charge-carrier balance is attained in rather hole-dominant PeLEDs. Meanwhile, BAEBi assisted to significantly mitigate the perovskite/ETL interfacial defects, rendering a pinhole-free smooth film with quite low roughness and ameliorated exciton lifetime. Consequently, BAEBi-containing NIR Q-2D PeLEDs manifested a low turn-on voltage of 2.5 V with a decent external quantum efficiency (EQE) of 9.2% and a peak radiance of 127 W sr −1 m −2 ; these values are, respectively, ∼1.5and 15-fold higher compared to that of a commonly used ETL, 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi). Importantly, the BAEBi-incorporating champion PeLED exhibited significantly curtailed efficiency roll-off and prolonged operational stability. These findings reveal an ingenious solution to address the charge imbalance issue and suppress the interfacial defects in PeLEDs that would spur further development of this emerging technology toward efficient solid-state lighting and high-resolution displays.

Metal Halide Perovskites: Promising Materials for Light-Emitting Diodes

“…The selection of suitable charge transportation layer materials is crucial for the formation of benign interfaces without inserting extra and complex modification materials. TPBi is a commonly used electron transportation layer material; however, it has a lower electron mobility than the hole mobility of materials generally used as hole transportation layer materials (such as PTAA and poly-TPD) [132][133][134][135]. Considering this case, Xu et al [136] synthesized new electron transportation layer materials, denoted as B2, to facilitate electron injection.…”

Balancing Charge Injection via a Tailor-Made Electron-Transporting Material for High Performance Blue Perovskite QLEDs

“…A classic device structure of a Pe-QLED is anode/hole injection layer/hole transport layer (HTL)/emission layer/electron transport layer (ETL)/electron injection later/cathode. Organic polymers, such as poly­[bis­(4-phenyl)­(2,4,6-trimethylphenyl)­amine] (PTAA) or poly­[ N , N ′-bis­(4-butylphenyl)- N , N ′-bis­(phenyl)­benzidene] (poly-TPD) are commonly used HTMs in Pe-QLEDs due to their high hole mobility exceeding 10 –3 cm 2 ·V –1 ·s –1 . , However, the electron mobility of widely used electron-transporting material (ETM) 1,3,5-tris­(1-phenyl-1 H -benzimidazol-2-yl)­benzene ( TPBi ) in Pe-QLEDs is approximately 1 × 10 –5 cm 2 ·V –1 ·s –1 , which is 2 orders of magnitude lower than the hole mobility of PTAA or poly-TPD. − This extremely nonequivalent charge carrier capacity of the two charge transport layers will make serious unbalanced charge injection in Pe-QLED devices. The excess charges triggered by the imbalanced charge injection accumulate at the interface, which would produce luminescence quenching through capture by defects or the Auger recombination process, thereby significantly hindering the device efficiency and stability. ,− In order to achieve fast and balanced carrier injection, ETMs with high electron mobilities, such as 4,6-bis­(3,5-di­(pyridine-3-yl)-2-methylpyrimidine (B3PYMPM) and 2,4,6-tris­[3-(diphenylphosphinyl)­phenyl]-1,3,5-triazine (PO-T2T) selected from the organic LEDs, have also been reported in Pe-QLEDs, and good device performance has been obtained.…”

Metal Halide Perovskite: A Promising Materials for Light Emitting Diodes

“…The selection of suitable charge transportation layer materials is crucial for the formation of benign interfaces without inserting extra and complex modification materials. TPBi is the commonly used electron transportation layer material, it, however, has lower electron mobility than hole mobility of generally used hole transportation layer materials (such as PTAA and poly-TPD) [126][127][128][129]. Considering the case, Xu et al [130] synthesized new electron transportation layer materials, denoted as B2, to facilitate the electron injection.…”