Efficient Perovskite Light‐Emitting Diodes Using Polycrystalline Core–Shell‐Mimicked Nanograins

Abstract

Making small nanograins in polycrystalline organic-inorganic halide perovskite (OIHP) films is critical to improving the luminescent efficiency in perovskite light-emitting diodes (PeLEDs). 3D polycrystalline OIHPs have fundamental limitations related to exciton binding energy and exciton diffusion length. At the same time, passivating the defects at the grain boundaries is also critical when the grain size becomes smaller. Molecular additives can be incorporated to shield the nanograins to suppress defects at grain boundaries; however, unevenly distributed molecular additives can cause imbalanced charge distribution and inefficient local defect passivation in polycrystalline OIHP films. Here, a kinetically controlled polycrystalline organic-shielded nanograin (OSN) film with a uniformly distributed organic semiconducting additive (2,2′,2′′-(1,3,5-benzinetriyl)-tris(1-phenyl-1-Hbenzimidazole), TPBI) is developed mimicking core-shell nanoparticles. The OSN film causes improved photophysical and electroluminescent properties with improved light out-coupling by possessing a low refractive index. Finally, highly improved electroluminescent efficiencies of 21.81% ph el −1 and 87.35 cd A −1 are achieved with a half-sphere lens and four-time increased half-lifetime in polycrystalline PeLEDs. This strategy to make homogeneous, defect-healed polycrystalline core-shell-mimicked nanograin film with better optical out-coupling will provide a simple and efficient way to make highly efficient perovskite polycrystal films and their optoelectronics devices.

Phenylalkylammonium passivation enables perovskite light emitting diodes with record high-radiance operational lifetime: the chain length matters

“… 25 ). Park et al introduced an organic semiconducting additive (2,2ʹ,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole), TPBi) in the precursor and proposed that a perovskite/organic core–shell structure is formed and accounts for the improvement of the stability 26 . Miao et al introduced benzylamine in the precursor and achieved PeLEDs with a T 50 of 23.7 h at a high current density of 100 mA cm −2 (ref.…”

Role of Capped Oleyl Amine in the Moisture‐Induced Structural Transformation of CsPbBr3 Perovskite Nanocrystals

“…The fascinating properties of lead halide perovskites such as broad absorption, narrow emission with near unity quantum yield, easier carrier extraction, and high photovoltaic efficiency proffered them as active materials for photovoltaic and light‐emitting applications . Till today, lead halide perovskite is one of the materials which has shown the highest efficiency for light‐emitting diodes (LEDs) and photovoltaic applications . These interesting properties of perovskites are mainly due to their peculiar crystal structures .…”

Blue-emission tuning of perovskite light-emitting diodes with a simple TPBi surface treatment

“…The additional peaks with wavenumbers in the range of 1250-1500 cm −1 can be ascribed to the fingerprint region of the C=N and C-N bondings of nitrogen heterocyclic rings in the benzimidazole part of TPBi. [22] Moreover, the broad peak at around 3000 cm −1 and the peak at 741.0 cm −1 can be assigned to the vibration of C-H in phenyl ring [23,24] and the C-S bond of TPBi, [24,25] respectively. No significant shifts were observed in these peak positions.…”

“…Consistently with this result, other groups demonstrated that TPBi did not chemically react with perovskite when it was used as an additive in the perovskite precursor solutions, which is due to the presence of relatively stronger Lewis bases of DMSO solvent. [22] Figure 3 shows the SEM images of the perovskite thin films with and without the treatments. The pristine perovskite film exhibited an extremely smooth surface with uniform and small grains [Fig.…”

“…This can be explained by the "impurity effect" in which the TPBi molecules intercalate into the grains which suppress continuous crystal growth of the perovskite. [22,27] We think that the increasingly inhomogeneous, rough perovskite films after the TPBi treatments together with the growing number of pinholes affect the charge transport, resulting in charge imbalance and nonradiative recombination, thus, causing the observed decrease of the overall device performance.…”