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Mixed Br/Cl perovskite nanocrystals (PeNCs) exhibit bright pure‐blue emission benefiting for fulfilling the Rec. 2100 standard. However, phase segregation remains a significant challenge that severely affects the stability and emission spectrum of perovskite light‐emitting diodes (PeLEDs). Here, we demonstrate the optimization of the spacing between polydentate functional groups of polymer ligands to match the surface pattern of CsPbBr1.8Cl1.2 PeNCs, resulting in effective synergistic passivation effect and significant improvements in PeLED performances. The block and alternating copolymers with different inter‐functional group spacing are facilely synthesized as ligands for PeNCs. Surprisingly, block copolymers with a higher functional group density do not match PeNCs, while alternating copolymers enable efficient PeNCs with the high photoluminescence intensity, low non‐radiative recombination rate and high exciton binding energy. Density functional theory calculations clearly confirm the almost perfect match between alternating copolymers and PeNCs. Finally, pure‐blue PeLEDs are achieved with the emission at 467 nm and Commission Internationale de l′Eclairage (CIE) coordinates of (0.131, 0.071), high external quantum efficiency (9.1 %) and record spectral and operational stabilities (~80 mins) in mixed‐halide PeLEDs. Overall, this study contributes to designing the polymer ligands and promoting the development of high‐performance and stable pure‐color PeLEDs towards display applications. [ABSTRACT FROM AUTHOR]

Advancing hole transport layers (HTL) to realize large‐area, flexible, and high‐performance perovskite solar cells (PSCs) is one of the most challenging issues for its commercialization. Here, a self‐assembled gradient Ti3C2Tx MXene incorporated PEDOT:PSS HTL is demonstrated to achieve high‐performance large‐area PSCs by establishing half‐caramelization‐based glucose‐induced MXene redistribution. Through this process, the Ti3C2Tx MXene nanosheets are spontaneously dispersed and redistributed at the top region of HTL to form the unique gradient distribution structure composed of MXene:Glucose:PEDOT:PSS (MG‐PEDOT). These results show that the MG‐PEDOT HTL not only offers favorable energy level alignment and efficient charge extraction, but also improves the film quality of perovskite layer featuring enlarged grain size, lower trap density, and longer carrier lifetime. Consequently, the power conversion efficiency (PCE) of the flexible device based on MG‐PEDOT HTL is increased by 36% compared to that of pristine PEDOT:PSS HTL. Meanwhile, the flexible perovskite solar minimodule (15 cm2 area) using MG‐PEDOT HTL achieve a PCE of 17.06%. The encapsulated modules show remarkable long‐term storage stability at 85 °C in ambient air (≈90% efficiency retention after 1200 h) and enhanced operational lifetime (≈90% efficiency retention after 200 h). This new approach shows a promising future of the self‐assembled HTLs for developing optoelectronic devices. [ABSTRACT FROM AUTHOR]

While there is promising achievement in terms of the power conversion efficiency (PCE) of perovskite solar cells (PSCs), long‐term stability has been considered the main obstacle for their practical application. In this work, the authors demonstrate the small monomer 2‐(dimethylamino) ethyl methacrylate (DMAEMA) with unsaturated carboxylic acid ester bond in the antisolvent for perovskite formation to improve the PCE and stability. The results show that DMAEMA is self‐polymerized and uniformly distributed in the film, contributing to the improved crystallinity of the perovskites. Equally important, it is found that there are newly established interactions of Pb2+ and DMAEMA, and iodine and ternary amine between DMAEMA and perovskites, which improves the uniformity of the lead (II) iodide vertical distribution along with the films and thus phase stability, as well as largely decreases defects density in the film. Overall, the inverted PSCs with DMAEMA exhibit a open‐circuit voltage of 1.10 V, short‐circuit current of 23.86 mA cm−2, fill factor of 0.82, and finally PCE reaches 21.52%. Meanwhile, the PSC stability is significantly improved due to the inhibition of the formation of iodine, reduction of the uncoordinated Pb2+, and suppression of phase segregation. [ABSTRACT FROM AUTHOR]

The physical and chemical properties of MXenes are strongly dependent on surface terminations; thus, the tailoring of surface functional groups in two-dimensional transition-metal carbides (MXenes) may extend the applicability of these compelling materials to a wider set of fields. In this work, we demonstrate the chemical modification of Ti 3 C 2 T x MXene via diazonium covalent chemistry and the subsequent effects on the electrical properties of MXene. The 4-nitrophenyl group was grafted onto the surface of MXene through a solid-liquid reaction, which was confirmed by various characterization methods, including X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, electron energy loss spectroscopy, atomic force microscopy, and transmission electron microscopy. The degree of modification of MXene is expediently tunable by adjusting the concentration of the diazonium salt solution. The work function of functionalized MXene is modifiable by regulating the quantity of grafted diazonium surface groups, with an adjustable range of around 0.6 eV. Further, in this study, the electrical properties of modified MXene are investigated through the fabrication of field-effect-transistor devices that utilize modified MXene as a channel material. It was demonstrated that with increasing concentration of 4-nitrophenyl groups grafted onto the surface the on/off current ratio of the modified MXene was improved to as much as 3.56, with a corresponding decrease in conductivity and mobility. The proposed approach of controlled modification of surface groups in Ti 3 C 2 T x may imbue Ti 3 C 2 T x with favorable electronic behaviors and demonstrate prospects for use in electronic field applications.