Novel Composite of Nickel Thiocyanate‐Based All‐Inorganic Lead Bromide Perovskite Nanocrystals with Enhanced Luminescent and Stability for White Light‐Emitting Diodes

Abstract

LEDs (WLEDs) based on PNCs has been replacing conventional lighting systems because of their high energy efficiency, long lifetime, low-power consumption, and environmental protection. [10] Despite their promising applications, several studies indicate that PNCs undergo severe degradation when exposed to air, moisture, and light for an extended time. [11] These environmental effects lead to a significant degree of surface defects, especially at the surfaces or grain boundaries of the PNCs that mediate the trap-assisted nonradiative losses. The trap-mediated losses lead to photoluminescence (PL) quenching, structural disorder, and low stability. Therefore, passivation of the defect states helps to obtain highly luminescent PNCs, which can exhibit better luminescence properties and higher stability. Various strategies have been employed to chemically passivate surface defects of PNCs, including surface coating with silica/ alumina or embedding in a polymer matrix, ligand engineering, and formation of a core-shell structure. [12][13][14][15] However, the encapsulation of PNCs in inorganic layers of silica and titania or core-shell structures deteriorates the optical performance of PNCs, which is characterized by large aggregates, broad spectra, and low PLQY. [13,16] Moreover, the applicability of PNCs blended with hydrophobic polymers such as poly(lauryl methacrylate) and polystyrene is relatively limited due to photo-oxidation of the polymers in the presence of ultraviolet (UV) light. [17] Besides, the ligand-exchange approach would still restrict the stability and structural integrity of PNCs due to the detachment of ligands during isolation, purification, and storage.More recently, studies have suggested that doping of metal ions (B or X-site), including transition metal ions and pseudohalide anions, positively affects the optoelectronic properties of perovskite structures. [18,19] In particular, doping can modify the energy formation, which improves the crystal quality and reduces crystal defects. [15] As a result, PNCs exhibiting higher luminescence efficiency and improved stability were obtained. The theoretical and experimental studies on Ni 2+ -doped CsPbX 3 PNCs showed that Ni 2+ doping the dopants essentially eliminates the structural defects of the PNCs due to the increased defect formation energy, improving the short-range ordering of the lattice, and providing remarkable PLQY. [20,21] Study has also shown that Zn 2+ -doped CsPbBr 3 NCs exhibit dramatically higher PLQY than pristine CsPbBr 3 NCs without any shift in the Doping of CsPbBr 3 perovskite nanocrystals (PNCs) to achieve excellent material properties is accelerating due to their increasing use in optoelectronic devices. Herein, a novel composite of CsPbBr 3 PNCs with nickel thiocyanate Ni(SCN) 2 is reported, exhibiting stronger photoluminescence (PL) and more extended stability. The addition of Ni(SCN) 2 at different molar concentrations reduces the surface trap states of the host PNCs. Therefore, the microstrain, dislocation density, PL emissio...

Thiocyanate-Stabilized Pseudo-cubic Perovskite CH(NH2)2PbI3 from Coincident Columnar Defect Lattices

“…Using molecular dynamics simulations, they demonstrated that the partial replacement of surface anions from I – to SCN – promotes the δ-to-α transition. It has also been reported that the addition of Pb­(SCN) 2 improves the grain size and photovoltaic efficiency of the thin films. , Improvement of the crystallinity of thin films by adding SCN – has also been discussed in two-dimensional perovskites and Cs-based perovskites. − Despite so much attention being paid to the effect of thiocyanate, it is still unclear how thiocyanate ions can integrate with the perovskite lattice and increase interfacial stability.…”

Solution-processed next generation thin film solar cells for indoor light applications

“…204 On the other hand, CsPbI 2 Br and CsPbBr 3 having bandgaps 1.92eV and 2.25 eV are comparatively quite stable and can be applicable for indoor applications. [205][206][207] As the phase stabilization of CsPbI 3 at ambient conditions has been a challenge, whereas CsPbI 2 Br provides better phase stability at room temperature and its bandgap is well matched to be used in indoor PSCs. 208 To avoid lead in indoor environment, a lot of research is going on in lead-free perovskite-inspired materials (PIMs) and these materials have greater stability in air ambient conditions.…”

“…204 On the other hand, CsPbI 2 Br and CsPbBr 3 having bandgaps of 1.92 eV and 2.25 eV are comparatively quite stable and can be used for indoor applications. [205][206][207] The phase stabilization of CsPbI 3 at ambient conditions has been a challenge, whereas CsPbI 2 Br provides better phase stability at room temperature and its bandgap is well suited for use in indoor PSCs. 208 Guo et al employed a new polymer, PDTDT, as a dopant-free HTM in CsPbI 2 Br solar cells and measured their performance in indoor light.…”