Wenfa Xie

Microcavity organic photodetectors (OPDs) utilize optical resonance to achieve wavelength-selective photodetection. Tailoring their spectral response requires understanding the interplay between cavity resonance and intrinsic material absorption. This work systematically controls microcavity resonance through layer thickness modulation and material selection to investigate its influence on spectral response. It demonstrates that employing a thick, strongly absorbing functional layer suppresses wide-angle and multibeam interference effects, thereby inhibiting spectral tunability. Cavity resonance tuning—essential for tailored spectral response—is only achievable by adjusting the cavity length via thickness control of a weakly absorbing functional layer, which facilitates interference between the two reflective electrodes. These results highlight the critical role of absorption management in microcavity OPD design and establish a systematic framework for optimizing spectral response through balanced cavity engineering and absorption control.

Flexible near‐infrared (NIR) organic light‐emitting diodes (OLEDs) face efficiency challenges due to low photoluminescence quantum yields (PLQYs) in NIR emitters, governed by the energy gap law. Accelerating radiative transitions via the Purcell effect in optical microcavities offers a solution, but conventional flexible semitransparent electrodes struggle to balance microcavity‐enhanced PLQY and light outcoupling efficiency (OCE). We address this with a micro‐structured magnesium‐bismuth (Mg‐Bi) alloy electrode offering 40% broadband transmittance (400–1600 nm) and conductivity (29.3 Ω ◻ ⁻¹ ). The alloy's low real permittivity supports less confined surface plasmon polariton and, with a capping layer, yields 60% NIR transmittance in an organic‐to‐air optical configuration. This design achieves 42.3% OCE and elevates the PLQY of a 704 nm NIR emitter to 71.8%, enabling flexible NIR‐OLEDs with a record 24.3% external quantum efficiency. The synergy of optical engineering and conductive microstructures establishes a universal strategy for high‐efficiency flexible NIR optoelectronics.

Metal halide perovskite light-emitting diodes (PeLEDs) have demonstrated excellent external quantum efficiency (EQE), easy colour tunability and low-cost processability, making them promising next-generation display techniques^1,2,3. However, PeLEDs still underperform compared with organic light-emitting diodes (LEDs) with an EQE of about 40% because of insufficient charge confinement and defect-caused non-radiative recombination on the film surface. Here we report a spontaneously formed 3D/2D vertically oriented perovskite heterojunction by means of a simple one-step spin-coating method, which could effectively confine the charge carriers and shift the radiation zone away from the defect-rich surface region. Notably, the 2D perovskite on top exhibits a wrinkled surface morphology, which offers up to 45.4% light extraction efficiency. The resulting PeLEDs achieved an EQE of 42.9% for the green emission (certified 42.3%). Our work sheds light on the strategies for fabricating high-efficiency PeLEDs in the future.

This study introduces a color-tunable organic light-emitting diode architecture based on a pixelated dual-microcavity design, fabricated using a single-layer mask technique. The device is engineered by vertically stacking a pixelated yellow emissive layer (EML) matrix onto a continuous, large-area blue EML. This configuration enables independent optical control of the blue and yellow emissions, resulting in narrowband spectra and high color purity that surpass the spectral modulation limitations inherent in conventional single-microcavity structures. To achieve near-monochromatic emission, a hole-dominant host was selected for the blue EML, while a bipolar host was employed for the pixelated yellow EML. A critical thickness differential between the regions with and without the yellow EML induces a distinct evolution in the intensity of blue and yellow emissions as a function of applied voltage. By exploiting voltage-driven carrier dynamics, the device exhibits continuous tuning of the International Commission on Illumination (CIE) coordinates from (0.19, 0.28) to (0.40, 0.47), thereby demonstrating outstanding and broadly controllable color gamut modulation.

Developing near-infrared (NIR) iridium(III) complexes with a narrowband emission remains a critical challenge for organic light-emitting diode (OLED) applications. Herein, two structurally simplified complexes, QT-Ir-Me and QT-Ir-tBu, featuring rigid cyclometalated ligands, are successfully developed. Both complexes exhibit deep-red/NIR phosphorescence with emission maxima at 692 nm for QT-Ir-Me and 706 nm for QT-Ir-tBu, with exceptionally narrow full width at half-maximum (FWHM) of 47 nm in a dilute solution. The suppressed spectral broadening can be assigned to dominated triplet ligand-centered charge transition in the excited state and constrained structural distortion, corroborated by minimal root-mean-square deviation of 0.089 and 0.084 for QT-Ir-Me and QT-Ir-tBu, respectively. Moreover, QT-Ir-Me and QT-Ir-tBu exhibit high photoluminescence quantum yields of 53% and 28%, respectively. The doped devices employing QT-Ir-Me and QT-Ir-tBu as emitters exhibit narrowband deep-red/NIR luminescence with FWHMs of 60 and 58 nm, respectively. A QT-Ir-Me-based device demonstrates higher electroluminescence performance with a maximum external quantum efficiency of 6.3%.

Logic circuits are a key link in the development from discrete organic thin-film transistors (OTFTs) to integrated circuits (ICs). The development of low-power and easy-to-manufacture logic circuits is an outstanding challenge for emerging flexible and wearable electronics. In this work, we propose a strategy for achieving flexible inverters by a facile manufacture process. The inverters integrate two identical ambipolar OTFTs in series, whose performances are optimized by engineering both gate dielectrics and bulk-heterojunction channels. The polystyrene (PS)/poly(methyl methacrylate) bilayer gate dielectric is employed to consider both mobility and operating voltage of OTFTs. Furthermore, the bulk-heterojunction channels, consisting of binary polymer semiconductors, are proposed and optimized to achieve balanced electronandhole mobilities. The optimal flexible OTFTs exhibit high and well-balanced electron and hole mobilities of $5.41\times 10^{-{2}}$ and $6.08\times 10^{-{2}}$ cm²/V $\cdot $ s, respectively. Furthermore, the high-performance complementary-like flexible inverter is achieved, with a high gain of 38.0 and good noise margin (NM) at a moderate operating voltage of 15 V. This work provides an efficient strategy for developing the potential practical flexible inverters that are manufactured by a facile process flow.

Quantum dot light‐emitting diodes (QLEDs) have emerged as a promising technology for display and lighting applications due to their high color purity, tunable emission wavelengths, and solution processability. However, carrier imbalance arising from differences in injection barriers and mobilities between electrons and holes remains a significant challenge, leading to charge accumulation or leakage and resulting in performance losses. To address these issues, exciton harvesting layers (EHLs) have recently gained attention as an effective and targeted strategy. This review presents a comprehensive overview of the EHL concept and its development in QLEDs. We begin by introducing the fundamental properties of quantum dots (QDs) and the working principles of QLEDs, followed by a discussion of the applicability of the EHL strategy. We then detail the mechanisms of energy transfer within EHL and between EHL and QDs, as well as its optimization approaches. Subsequently, we summarize the application of EHLs in QLEDs and the corresponding improvements in device performance. Finally, we highlight current challenges and future research directions of the EHL strategy.