Unveiling the additive-assisted oriented growth of perovskite crystallite for high performance light-emitting diodes

Abstract

Solution-processed metal halide perovskites have been recognized as one of the most promising semiconductors, with applications in light-emitting diodes (LEDs), solar cells and lasers. Various additives have been widely used in perovskite precursor solutions, aiming to improve the formed perovskite film quality through passivating defects and controlling the crystallinity. The additive’s role of defect passivation has been intensively investigated, while a deep understanding of how additives influence the crystallization process of perovskites is lacking. Here, we reveal a general additive-assisted crystal formation pathway for FAPbI3 perovskite with vertical orientation, by tracking the chemical interaction in the precursor solution and crystallographic evolution during the film formation process. The resulting understanding motivates us to use a new additive with multi-functional groups, 2-(2-(2-Aminoethoxy)ethoxy)acetic acid, which can facilitate the orientated growth of perovskite and passivate defects, leading to perovskite layer with high crystallinity and low defect density and thereby record-high performance NIR perovskite LEDs (~800 nm emission peak, a peak external quantum efficiency of 22.2% with enhanced stability).

Toward Stable and Efficient Perovskite Light‐Emitting Diodes

“…[10,12,13,50] The maximum EQEs for perovskite LEDs with standard thin-film LED structures were expected to be around 10-15% due to the relatively large refractive indices of the perovskite EMLs. [50] However, the EQEs of PeLEDs have exceeded 20% [4][5][6][7][12][13][14]50,54,71,72,82,90,91,93] in recent years. Cho et al [50] demonstrated that this enhancement may be partly attributed to photon recycling which could contribute 30-70% of the overall EL, especially for perovskites with large absorption-emission spectral overlaps.…”

Aggregation Control, Surface Passivation, and Optimization of Device Structure toward Near‐Infrared Perovskite Quantum‐Dot Light‐Emitting Diodes with an EQE up to 15.4%

“…Since the first report of perovskitebased LEDs in 2014, [8][9][10] 3D perovskite film-based NIR-I LEDs have been developed using several methods, such as surface passivation and by employing optimum hole-transporting materials, affording external quantum efficiencies (EQEs) of >20% [11][12][13][14] in just a few short years of development. To further improve the image contrast, a narrow full width at half maximum (FWHM) of the emitting light is a key issue for efficiently filtering out the excitation light.…”

Reciprocally Photovoltaic Light‐Emitting Diode Based on Dispersive Perovskite Nanocrystal

“…The external quantum efficiencies (EQEs) of PeLEDs increased from 0.76% to 23.4% for green light, 12.3% for blue light, 22.2% for near-infrared light, and the power conversion efficiency (PCE) of PSC also improved from 3.8% to 25.5%, such rapid research progress has undoubtedly promoted the vigorous development of perovskite materials. [1][2][3][4][5][6][7][8] TFB as hole transport layer (HTL) to engineer the charge injection and extraction. We obtained a bifunctional device with an EQE EL of 23.2% with a brightness of 490 W sr −1 m −2 at 2.7 V under PeLED operation and a PVE of 15.2% when operated as PSC.…”

“…The external quantum efficiencies (EQEs) of PeLEDs increased from 0.76% to 23.4% for green light, 12.3% for blue light, 22.2% for near‐infrared light, and the power conversion efficiency (PCE) of PSC also improved from 3.8% to 25.5%, such rapid research progress has undoubtedly promoted the vigorous development of perovskite materials. [ 1–8 ]…”