Increasing the Performance and Stability of Red-Light-Emitting Diodes Using Guanidinium Mixed-Cation Perovskite Nanocrystals

Abstract

Halide perovskite nanocrystals (PNCs) exhibit growing attention in optoelectronics due to their fascinating color purity and improved intrinsic properties. However, structural defects emerging in PNCs progressively hinder the radiative recombination and carrier transfer dynamics, limiting the performance of light-emitting devices. In this work, we explored the introduction of guanidinium (GA + ) during the synthesis of high-quality Cs 1−x GA x PbI 3 PNCs as a promising approach for the fabrication of efficient bright-red light-emitting diodes (R-LEDs). The substitution of Cs by 10 mol % GA allows the preparation of mixed-cation PNCs with PLQY up to 100% and long-term stability for 180 days, stored under air atmosphere and refrigerated condition (4 °C). Here, GA + cations fill/replace Cs + positions into the PNCs, compensating intrinsic defect sites and suppressing the nonradiative recombination pathway. LEDs fabricated with this optimum material show an external quantum efficiency (EQE) near to 19%, at an operational voltage of 5 V (50−100 cd/m 2 ) and an operational half-time (t 50 ) increased 67% respect CsPbI 3 R-LEDs. Our findings show the possibility to compensate the deficiency through A-site cation addition during the material synthesis, obtaining less defective PNCs for efficient and stable optoelectronic devices.

Non‐Resonant Barrier Excitation in Conjugated Aromatic Ligand‐Modified Perovskite Quantum Dots Enables a High Quantum Efficiency

“…Because A‐cation (Cs + ) hardly contributes to the band–edge construction and radiative transition process, modifying A‐cation is supposed to become the effective approach to fine‐tune thermodynamic or kinetic stabilization, interfacial weak interactions, and surface functionalization. [ 8c,17 ] As our synthesis strategy has substantially reduced the proportion of Cs‐oleate and over‐feeding PbI 2 precursor, A‐cation defection ( V A ) is prospectively dominated in our CsPbI 3 QDs. As it is known, this composition‐dependent defect type is unlikely to degrade the optoelectronic properties of CsPbI 3 QDs, [ 18 ] and CsI‐terminations are considered as the major surface termination of CsPbI 3 .…”

Impact of core–shell perovskite nanocrystals for LED applications: successes, challenges, and prospects

“…The benets of guanidium cations are attributed to their strong hydrogen bonding ability with the surface halides, which in turn facilitates the surface defect recovery. [58][59][60][61] 3D/2D core/shell perovskites are regarded as multidimensional perovskites, where Chen et al revealed that the multidimensional type-I heterostructure formation between 3D MAPbBr 3 and 2D (octylammonium) 2 PbBr 4 leads to multiphoton absorption, which are useful for multiphoton imaging applications. 62 In a recent report by Ye et al, 25 spin-polarised luminescence behaviour has been studied, where a chiral organic ammonium bromide molecule is introduced to provide a 2D perovskite layer coating, which formed a 3D/2D core/shell with a type-II heterostructure.…”

Microwave-Mediated Synthesis of Lead-Free Cesium Titanium Bromide Double Perovskite: A Sustainable Approach

“…Metal halide perovskite materials with ABX 3 stoichiometry (for example, with A: CH 3 NH 3 + or Cs + , B: Pb 2+ , X: I – or Br – ) and their derivates such as double metal halide perovskites with A 2 BX 6 formulas have recently received significant attention, particularly for their demonstrated potential for photovoltaics and other optoelectronic applications. These materials have excellent properties like bandgap tunability, structural flexibility, and remarkable charge transport properties, resulting in excellent device performances. − Power conversion efficiencies (PCEs) of lead-based perovskite solar cells (PSCs) reached up to 26.1% in 2023 equivalent to commercial solar cells and keep rising yearly . Furthermore, the affordability and accessibility of perovskite materials significantly encourage the development of the technology for commercial purposes .…”