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Novel carbene‐based tetradentated Pt(II) complexes, namely Pt(pibOppy) and Pt(ppbOppy), are developed and found to exhibit radiative metal‐centered (MC) d‐p triplet transition, resulting in highly efficient and configurational‐rigid phosphorescence. The Pt(II) complexes emit green light with peak wavelengths of 512–526 nm. Pt(ppbOppy), with enhanced carbene‐Pt interaction, achieves a high photoluminescent quantum yield of 99% in thin film, better thermo‐ and photo‐stability, and a structured emission spectrum. Device B1, by incorporating Pt (ppbOppy), shows a narrow green emission with Commission Internationale de l'Elcairage (CIE) coordinates of (0.306, 0.633), a long working lifetime of LT95 = 111 h at 1000 cd m−2, and high maximum values of the external quantum efficiency, power efficiency, and current efficiency of 20.4%, 74.1 lm W−1, and 72.1 cd A−1, respectively. The exceedingly flawless device performance highlights the immense potential of Pt(II) complexes with d‐p transition for organic electroluminescence. [ABSTRACT FROM AUTHOR]

The rapid development of lead halide perovskite light emitting diodes (PeLED) provides bright prospects for future lighting and display applications. However, the lack of efficient blue light emission, the insufficient device stability, and the shortage of convenient patterning methods greatly impede the development of PeLED applications. In this work, a feasible two‐step fabrication method combined with a block copolymer (BCP) template is introduced to fabricate high quality CH3NH3PbBrxCl3−x 3D perovskite film. The BCP‐templated CH3NH3PbBr3 film possesses a state‐of‐the‐art photoluminescence quantum yield (PLQY) of 62% in the champion sample (58% average PLQY) and an outstanding stability at room temperature. Using halide‐free lead acetate trihydrate as the lead source, the color of the photoluminescence can be tuned easily from green to blue by simply controlling the Cl/Br ratio in the second step. A sky‐blue emission is obtained from a CH3NH3PbBr1.5Cl1.5 perovskite film with a PLQY of 23 ± 2%. The two‐step fabrication approach can also enable straightforward patterning, as demonstrated with inkjet printing and Chinese calligraphy. [ABSTRACT FROM AUTHOR]

Abstract: We explore in this work the use of Cu as a cathode material in organic light-emitting devices (OLEDs) and find a dual electron–injection enhancement mechanism derived from the LiF layer. Different from what observed previously in Ag- and Au-cathode devices, the LiF buffer layer in the Cu-cathode OLEDs starts to play its role in performance improvement when it is much thinner than 3nm, the optimal value of buffer thickness, and in the case of optimal thickness, the device exhibits excellent performance comparable to conventional Al-cathode device. The phenomenon observed is ascribed to enhanced electron injection as a result of combined effect of interfacial reaction and tunneling barrier reduction mechanism: while chemical reaction plays a key role at the very beginning of interface formation, tunneling dominates in the subsequent stage leading to the tremendous improvement of the characteristics. [Copyright &y& Elsevier]