Color-Stable and High-Efficiency Blue Perovskite Nanocrystal Light-Emitting Diodes via Monovalent Copper Ion Lowering Lead Defects

Abstract

Light-emitting diodes using metal halide perovskite (PeLEDs) exhibit a strong potential for emerging display technologies due to their unique optoelectronic characteristics. However, for blue emission PeLEDs, there remains a huge challenge to achieve high performance, an issue that has been addressed in their red and green counterparts. The community is circumventing the challenges in synthesizing stable, high-quantum-efficiency, and low-defect-density blue emitters. Here, a facile strategy that replaces Pb by adding a monovalent ion Cu + , in this case into CsPbClBr 2 perovskite, is carried out. This decreases the Pb dangling bonds and increases the radiative recombination for the enhancement of blue emission. The nanoparticles obtained by this method maintain a blue emission at 479 nm. The photoluminescence quantum yield is 2 times higher than the pristine analogue. The corresponding perovskite nanocrystal (PNC) LEDs achieve stable electroluminescence spectrum at high brightness. Simultaneously, the optimal blue PNC LEDs obtain the maximum values of luminance and external quantum efficiency of 1537 cd m −2 and 3.78%, respectively. And the device realizes typical blue light CIE chromaticity coordinates of (0.098, 0.123). Our work reveals that the substitution of Pb by heterovalent ions significantly decreases nanocrystal defects, which will pave the way of perovskite LEDs for practical applications in the future.

Thiophene Derivatives as Ligands for Highly Luminescent and Stable Manganese-Doped CsPbCl3 Nanocrystals

“…Based on these results, we propose a passivation mechanism of defects (Figure 3A). In the pristine Mn: CsPbCl 3 perovskites, there are various structure defects (such as chloride vacancy) at the surface of the NCs (Yang et al, 2020) (Zhang Y. et al, 2021). After the addition of TBA, the under-coordinated Pb ions in the perovskite NCs form Pb-S bonds with the S atoms of the thiophene in TBA, thus passivating the surface defects and decreasing non-radiative recombination, enabling the material to improve its performance.…”

“…Currently, ion doping and ligand modification are two main strategies to improve the PLQY and the stability of perovskite NCs ( Luo et al, 2019 ; Gao et al, 2021 ). Specifically for Mn: CsPbCl 3 NCs, in terms of ion doping, alkaline earth metals (Ca 2+ , Mg 2+ , and Ba 2+ ) ( Liu W. et al, 2018 ; Song et al, 2020 ), transition metals (Ni 2+ , Cd 2+ , and Cu 2+ ) ( Wang et al, 2019a ; Rana et al, 2019 ; Xing et al, 2019 ; Zhao Y. et al, 2020 ; Cao et al, 2020 ; Ricciarelli et al, 2020 ; Zheng et al, 2020 ; Zhou et al, 2020 ; Zhang R. et al, 2021 ), and rare-earth ions (Yb 3+ , Eu 2+ , and Tm 3+ ) ( Wang et al, 2019b ; Milstein et al, 2019 ; Zhao J. et al, 2020 ) have been introduced into perovskite NCs to effectively passivate defects and improve PLQYs.…”

A mixed solvent strategy enabling efficient all-solution-processed perovskite light-emitting diodes

“…where I represents the normalized PL intensity, A 1 and A 2 are the fractions of the two decay components, and t 1 and t 2 are the lifetimes of the two decay components, respectively. 29 Table S1 (ESI †) summarizes the detailed fitting parameters.…”

“…All the TRPL decay curves can be fitted with the biexponential function as follows: I = A 1 e − x / τ 1 + A 2 e − x / τ 2 where I represents the normalized PL intensity, A 1 and A 2 are the fractions of the two decay components, and τ 1 and τ 2 are the lifetimes of the two decay components, respectively. 29 Table S1 (ESI†) summarizes the detailed fitting parameters. In our case, A 1 represents the monomolecular non-radiative trap-assisted recombination decay component and A 2 represents the bimolecular radiative recombination decay component.…”

Intercalate Superconductivity and van der Waals Equation

“…Usually this is not the case. For example, for copper and oxygen, the former is often treated as either a divalent or monovalent element, , and the latter is typically framed as a “hole dopant” . Neither of these scenarios were considered when employing the ideal gas law at the onset or when using the van der Waals equation to estimate the gap (summarized in Figure ).…”