Xinwen Zhang

Degradable AgNWs composite electrodes with outstanding optoelectrical properties and mechanical stability were fabricated by adopting a natural eco-friendly material of gum arabic as a modification layer.

Efficient blue quasi-2D perovskite light-emitting diodes were developed by introducing disodium pyrophosphate as an additive into the precursor solution to passivate uncoordinated Pb ²⁺ and regulate the phase distribution.

Flexible optoelectronic devices play a crucial role in the field of wearable electronics. However, their potential and development have been hindered by the lack of high-performance and durable flexible transparent electrodes. Here, we developed ultrathin Ag mesh electrodes using a direct writing technique by a Chinese brush. Through precise control over the writing process, the printed Ag mesh with an ultrathin thickness of ~100 nm and a high width resolution of ~20 µm was achieved. The resulted composite electrodes of Norland Optical Adhesive 63 (NOA63)/Ag mesh/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) possess a low sheet resistance of ~12 Ω/sq and a high transmittance of ~91%. Benefiting from the ultrathin Ag mesh and embedded structure, the composite electrode shows the quite low surface roughness (~0.9 nm), along with exceptional mechanical flexibility with a micrometer-scale bending radius. Furthermore, stretchable organic light-emitting devices (OLEDs) based on this composite electrode present an impressive current efficiency of 88.6 cd/A. Significantly, the OLEDs remain 86% initial current efficiency over 1000 bending cycles, and maintain 88% initial luminance at the 50% strain. Interestingly, this direct writing technique possesses the remarkable capability to print transparent electrodes on curved or uneven substrate surfaces, expanding its potential for universal applications. This work presents a straightforward and general printing method for constructing high-performance flexible transparent electrodes for various flexible electronics.

Circularly polarized organic light-emitting diodes (CP-OLEDs) hold significant promise for 3D displays owing to their ability to directly emit circularly polarized light. However, achieving multicolor circularly polarized electroluminescence requires synthesizing and separating luminescence enantiomers with different emission wavelengths, greatly increasing manufacturing complexity and costs. In contrast, chiral hole transport materials present a straightforward and versatile strategy for achieving various high-performance CP-OLEDs. In this work, two pairs of chiral hole transport materials, R/S-CzTPA and R/S-BuCzTPA, were synthesized using R/S-1,1′-binaphthyl-2,2′-diamine as a chiral precursor. These compounds also integrate carbazole and triarylamine functional groups, combining efficient hole transport properties with axial chirality. The hole mobilities for R-CzTPA and R-BuCzTPA are measured as 5.63 × 10⁻⁵ and 2.72 × 10⁻⁶ cm² V⁻¹ s⁻¹ (E = 0.4 MV cm⁻¹), respectively. Additionally, these materials exhibit strong circularly polarized luminescence with dissymmetry factors (|g_lum|) of up to 5.7 × 10⁻³/2.5 × 10⁻³ in toluene and 3.6 × 10⁻³/1.9 × 10⁻³ in films, alongside excellent thermal stability. Notably, green CP-OLEDs are fabricated using R/S-CzTPA as the chiral hole transport layer and tris(2-phenylpyridine)iridium(III) as the achiral phosphorescent emitter, achieving the maximum luminance of 94 449/93 661 cd m⁻², the maximum current efficiency of 62/61 cd A⁻¹, the maximum external quantum efficiency of 19/18%, and an electroluminescence dissymmetry factor of −1.2 × 10⁻³/+1.6 × 10⁻³.

The phenomenon of chiral symmetry breaking during the crystallization of achiral molecules or ions, which leads to the formation of controllable enantiomerically pure crystals, has garnered significant interest but remains a challenge to fully overcome. This presents a particularly formidable obstacle in the creation of three-dimensional (3D) structured chiral all-inorganic perovskites, further complicated by their achiral crystalline space groups. In this report, we successfully synthesized right- or left-handed (P/M) chiral 3D P/M-CsPbX₃ (X = Cl, Cl-Br, Br, Br-I) perovskite subnanowires (SNWs), in which Pb(II) can be partially substituted by hetero ions, such as Cu(II), Sn(II), and Mn(II). The selective control of the SNW handedness was achieved through the strategic incorporation of trace chiral amine enantiomers. The chiroptical activity arises from the helical structure of the SNWs. The mechanisms underlying the formation of this chiral structure were systematically investigated and interpreted by using a thermodynamic model. We utilized the chiral P/M-CsPbBr₃ SNWs to fabricate circularly polarized light (CPL) photodetectors, which exhibited an impressive photocurrent dissymmetry factor (g_Iph) of 0.75. In the field of spin light-emitting diodes (spin-LEDs), circularly polarized electroluminescence (CPEL) was accomplished by employing the SNWs as a dual-functional material that provides both chiral-induced spin selectivity (CISS) and CPL emission capabilities.

Herein, a Y-type compound (67dMeOTPA-FQ) and a T-type compound (58dMeOTPA-FQ) based on furo[2,3-b]quinoxaline were synthesized. The theory calculation shows the S₁ and T₁ of both compounds own a charge-transfer feature while their T₂ states have a local excitation feature. The calculated k_RISC(T2-S1) is one to 2 orders of magnitude larger than k_RISC(T1-S1). Thus, the nonadiabatic spin-vibronic mechanism involved in the T₂ state is suggested to be responsible for the thermally activated delayed fluorescence (TADF) feature. Meanwhile, when 2-methyl-9,10-bis(naphthalen-2-yl)anthracene is selected as host, the maximum luminance of the device based on 67dMeOTPA-FQ is up to 104215 cd·m^-2, and the external quantum efficiency (EQE) keeps in the 8.2-8.0% range with the luminance changed from 55.0 cd·m^-2 to 90000 cd·m^-2, only 2.4% efficiency roll-off. As for 58dMeOTPA-FQ, a slightly lower EQE of 7.1-6.7% with the luminance range of 1-40000 cd·m^-2 was achieved for orange-red emission. Both the reverse intersystem crossing (RISC) and triplet-triplet annihilation mechanisms are supposed to concurrently contribute to the utilization of triplet excitons and suppress the notorious efficiency roll-off observed in TADF-based devices.

All inorganic metal halide perovskite nanocrystals (NCs) have attracted much attention for their outstanding optoelectronic properties, which can be tuned by the composition, surface, size and morphology in nanoscale. Herein, we report the microfluidic synthesis of hollow CsPbBr₃ perovskite NCs through the nanoscale Kirkendall effect. The formation mechanism of the hollow structure (Kirkendall void) controlled by the temperature, flow rate, ratios of precursors and ligands was investigated. Compared with the solid CsPbBr₃ NCs of the same size, the hollow CsPbBr₃ NCs exhibit blue shifts in ultraviolet–visible (UV–vis) absorption and photoluminescence (PL) spectra, and remarkably longer PL average lifetime (~ 98.2 ns). Quantum confinement effect, inner surface induced additional trap states and lattice strain of the hollow CsPbBr₃ NCs were discussed in understanding their unique optoelectronic properties. The hollow CsPbBr₃ NC based photodetector exhibits an outstanding negative photoconductivity (NPC) detectivity of 8.9 × 10¹² Jones. They also show potentials in perovskite NC based photovoltaic and light emitting diodes (LEDs).