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Metal halide perovskite light-emitting diodes (PeLEDs) have been recognized as emerging candidates for next-generation solution-processed electronic display technology, and great progress has been made in recent years. However, their poor operational stability is yet to be solved. Here, we present a reformative all-inorganic red-emission PeLED based on the passivation effect caused by the incorporation of zinc ions into perovskites for enhancing the efficiency and operational stability. A high-quality quasi-two-dimensional perovskite CsPbI3−xBrx thin film with good crystallinity is obtained, benefiting from the combination of large organic ammonium ions (PEA+ ions) and inorganic salt zinc iodide (ZnI2). As a result, ZnI2-passivated CsPbI3−xBrx PeLEDs emitting at 666 nm show a maximum external quantum efficiency of 9.93% and a maximum brightness of 4258 cd m−2. More importantly, the PeLEDs achieve a long half-lifetime of about 2667 h at an initial luminance of 100 cd m−2. This work provides a facile method to obtain stable and efficient red-emission PeLEDs.

Organic-inorganic hybrid lead halide perovskites are potential candidates for next-generation light-emitting diodes (LEDs) in terms of tunable emission wavelengths, high electroluminescence efficiency, and excellent color purity. However, the device performance is still limited by severe non-radiative recombination losses and operational instability due to a high degree of defect states on the perovskite surface. Here, an effective surface engineering method is developed via the assistance of guanidinium iodide (GAI), which allows the formation of surface-2D heterophased perovskite nanograins and surface defect passivation due to the bonding with undercoordinated halide ions. Efficient and stable red-emission LEDs are realized with the improved optoelectronic properties of GAI-modified perovskite nanograins by suppressing the trap-mediated non-radiative recombination loss. The champion device with a high color purity at 692 nm achieves an external quantum efficiency of 17.1%, which is 2.3 times that of the control device. Furthermore, the operational stability is highly improved, showing a half-lifetime of 563 min at an initial luminance of 1000 cd m-2. The proposed GAI-assisted surface engineering is a promising approach for defect passivation and phase engineering in perovskite films to achieve high-performance perovskite LEDs.

Although perovskite light-emitting diodes (PeLEDs) are promising for next-generation displays and lighting, their efficiency is still considerably below that of conventional inorganic and organic counterparts. Significant efforts in various aspects of the electroluminescence process are required to achieve high-performance PeLEDs. Here, we present an improved flexible PeLED structure based on the rational interface engineering for energy-efficient photon generation and enhanced light outcoupling. The interface-stimulated crystallization and defect passivation of the perovskite emitter are synergistically realized by tuning the underlying interlayer, leading to the suppression of trap-mediated nonradiative recombination losses. Besides approaching highly emissive perovskite layers, the outcoupling of trapped light is also enhanced by combining the silver nanowires-based electrode with quasi-random nanopatterns on flexible plastic substrate. Upon the collective optimization of the device structure, a record external quantum efficiency of 24.5% is achieved for flexible PeLEDs based on green-emitting CsPbBr3 perovskite.

White organic light-emitting diodes (WOLEDs) using thermally activated delayed fluorescence (TADF)-based single emissive layer (SEL) have attracted enormous attention because of their simple device structure and full exciton utilization potential for high efficiency. However, WOLEDs made of an all-TADF SEL usually exhibit serious efficiency roll-off and poor color stability due to serious exciton-annihilation and unbalanced radiative decays of different TADF emitters. Herein, a new strategy is proposed to manipulate the TADF-sensitized fluorescence process by combining dual-host systems of high triplet energy with a conventional fluorescent emitter of complementary color. The multiple energy-funneling paths are modulated and short-range Dexter energy transfer is largely suppressed due to the steric effect of peripheral tert-butyl group in the blue TADF sensitizer. The resulting all-fluorescent WOLEDs achieve an unprecedentedly high external quantum efficiency of 21.8% with balanced white emission of Commission Internationale de l'Eclairage coordinate of (0.292, 0.343), accompanied with good color stability, reduced efficiency roll-off, and prolonged operational lifetime. These findings demonstrate the validity of this strategy for precisely allocating the exciton harvesting in SEL WOLEDs.

High-efficiency orange and red thermally activated delayed fluorescent (TADF) organic light-emitting diodes were fabricated based on a pair of isomers 3,6,11-triAC-BPQ and 3,6,12-triAC-BPQ, containing a rigid dibenzo[f,h]pyrido[2,3-b]quinoxaline (BPQ) core and three 9,9-dimethyl-9,10-dihydroacridine (Ac) donors. Both materials exhibited red emission in neat films and small singlet–triplet energy gaps. Compared with the stable intramolecular charge transfer (ICT) state of 3,6,12-triAC-BPQ, 3,6,11-triAC-BPQ showed hybridized local and charge transfer (HLCT) character due to the H-bond between the 11-position Ac and 10-position N atom. As a result, the doped film of 3,6,11-triAC-BPQ showed a high photoluminescence quantum yield (PLQY) and the related device showed a high external quantum efficiency (EQE) of 22.0% in the orange–red region.

Exploiting effective orange-red thermally activated delayed fluorescent (TADF) emitters is still challenging. In this work, we proposed a method by using a crooked donor (D) moiety instead of its conventional planar form to balance the opposite influences of frontier molecular orbital overlap on the reverse intersystem crossing and the singlet radiative decay rate. A novel orange-red TADF emitter, named 2-(4-(9,9-dimethyl-4-phenylacridin-10(9H)-yl)phenyl)anthracene-9,10-dione (AQ-PhDMAC), was accordingly designed and synthesized. Owing to the steric effect of the α-phenyl ring in 9,9-dimethyl-4-phenyl-9,10-dihydroacridine (α-PhDMAC), a relatively small singlet–triplet energy splitting of 0.22 eV and a high fluorescence quantum yield of 0.89 can be realized simultaneously. The orange-red organic light-emitting diode based on AQ-PhDMAC exhibited a maximum external quantum efficiency of 18.1%, much improved compared with the 13.7% efficiency of the α-phenyl ring-free control emitter (AQ-DMAC). These results propose a new viewpoint that enforcing crooked D segments by large steric hindrance actually has a great potential for applications in orange-red TADF molecular design, to improve their electroluminescence efficiency.

While tremendous progress has recently been made in perovskite light‐emitting diodes (PeLEDs), large‐area blue devices feature inferior performance due to uneven morphologies and vast defects in the solution‐processed perovskite films. To alleviate these issues, a facile and reliable interface engineering scheme is reported for manipulating the crystallization of perovskite films enabled by a multifunctional molecule 2‐amino‐1,3‐propanediol (APDO)‐triggered “anchoring effect” at the grain‐growth interface. Sky‐blue perovskite films with large‐area uniformity and low trap states are obtained, showing the distinctly improved radiative recombination and hole‐transport capability. Based on the APDO‐induced interface engineering, synergistical boost in device performance is achieved for large‐area sky‐blue PeLED (measuring at 100 mm2) with a peak external quantum efficiency (EQE) of 9.2% and a highly prolonged operational lifetime. A decent EQE up to 6.1% is demonstrated for the largest sky‐blue device emitting at 400 mm2., A facile and effective grain‐growth manipulation scheme enabled by interface “anchoring effect” is proposed for high‐quality sky‐blue perovskite emitter. Remarkable boost in device performance is achieved for large‐scale sky‐blue perovskite LEDs with peak external quantum efficiencies of 9.2% and 6.1% measured at scales of 100 and 400 mm2, respectively.

Thermally activated delayed fluorescence (TADF) emitters with aggregation-induced emission (AIE) features are hot candidates for non-doped organic light-emitting diodes (OLEDs), as they are highly emissive in solid states upon photoexcitation. Nevertheless, not every AIE-TADF emitter in the past had guaranteed decent efficiencies in non-doped devices, indicating that the AIE character alone does not necessarily afford ideal non-doped TADF emitters. As intermolecular electron-exchange interaction that involves long-lived triplet excitons plays a dominant role in the whole quenching process of TADF, we anticipate that it is the main reason for the different electroluminescence performances of AIE-TADF emitters. Therefore, in this work, we designed two TADF emitters SPBP-DPAC and SPBP-SPAC by modifying a reported less successful emitter BP-DPAC with extra fluorenes to increase intermolecular distances and attenuate this electron-exchange interaction. With the fluorene lock as steric hindrance, SPBP-DPAC and SPBP-SPAC exhibit significantly higher exciton utilization in non-doped films due to the suppressed concentration quenching. The non-doped OLEDs based on SPBP-DPAC and SPBP-SPAC show an excellent maximum external quantum efficiency (EQE) of 22.8% and 21.3% respectively, and what's even more promising is that ignorable roll-offs at practical brightness (e.g., 1000 and 5000 cd m−2) were realized. These results reveal that locking the phenyl rings as steric hindrance can not only enhance the molecular rigidity, but also cause immediate relief of concentration quenching, and result in significant performance improvement under non-doped conditions. Our approach proposes a feasible molecular modification strategy for AIE-TADF emitters, potentially increasing their applicability in OLEDs., Two TADF emitters were developed by modifying a reported less successful emitter BP-DPAC with fluorene to suppress concentration quenching. Their non-doped OLEDs displayed excellent EQEs of 22.8% and 21.3% with well-suppressed roll-off.

An electron-rich moiety, pyrrolo[3,2-b]pyrrole, has been used as a new donor block in organic lighting-emitting diodes (OLEDs). Combined with a strong electron-withdrawing group of 2,1,3-benzothiadiazole, a novel red fluorophore BTZPP was synthesized. The solution-processed red-emitting device based on BTZPP showed encouraging performances with external quantum efficiency of up to 3.4%. This evidently indicates that the pyrrolo[3,2-b]pyrrole group can be a promising electron-donating moiety for enriching the material types and promoting the development of OLEDs.

All-inorganic CsPbBr3 perovskite quantum dots (QDs) hold great promise as candidate materials for next-generation electroluminescent displays owing to their excellent optoelectronic properties. However, the long insulating ligands on the surface of CsPbBr3 QDs originating from the synthesis process hinder the fabrication of high-performance optoelectronic devices. Herein, an efficient ligand-exchange route is proposed with the use of perovskite-precursor-based halide ligands, including a series of phenalkylammonium bromides with a π-conjugation benzene ring and different branch lengths. Based on the ligand-exchange method, the conductivity of the CsPbBr3 QD layer is significantly improved owing to ligand shortening and the insertion of the π-conjugation benzene ring. As a result, high brightness (up to 12,650 cd/m2) and low turn-on voltage (as low as 2.66 V) can be realized in CsPbBr3 QD light-emitting diodes (QLEDs), leading to dramatic improvements in device performance with a current efficiency of 13.43 cd/A, power efficiency of 12.05 lm/W, and external quantum efficiency of 4.33%.

Perovskite light-emitting diodes (PeLEDs) are promising for full-color displays due to their high color purity, low-cost and solution processability. However, pure-red PeLEDs still lag behind their green and deep-red counterparts in efficiency and brightness. Here, we employ three structurally similar dual-Lewis-base molecules ethylenediamine, ethanolamine and beta-alanine to modify the interface between the hole transport layer (HTL) and (Cs/K/PEA)PbI3-xBrx perovskite layer for efficient pure-red PeLEDs. The functional groups in these molecules can enhance the hydrophilicity on the surface of the HTL, which improves the perovskite film quality and inhibits the formation of unfavorable low-order (n = 1 and n = 2) phases. Besides, amino groups can coordinate with interfacial defects. In particular, ethanolamine and beta-alanine enable the strong film growth modulation and passivation effect due to the presence of hydroxyl and carboxyl groups. The perovskites based on ethanolamine and beta-alanine interfacial modification give rise to enhanced photoluminescence quantum yields of up to 36.5% and 34.4%, respectively. Consequently, the optimal PeLEDs achieve a pure-red emission at 634 nm with a maximum luminance of 9218 cd m−2 and a peak external quantum efficiency of 5.27%.

The development of efficient long-wavelength TADF emitters has been full of challenges owing to the various strict molecular design limiting factors. Herein, two orange-red TADF emitters, namely 3DMAC-BP-Br and 3DMAC-BP-CN, based on donor 9,9-dimethyl-9,10-dihydroacridine (DMAC) and rigid acceptor dibenzo[a,c]phenazine (BP) modified by electron-withdrawing bromine atom or cyano group, were designed and synthesized. Both emitters have large twisted D-A-D structure. The strong electron-withdrawing capabilities of the bromine atom or cyano group can dramatically affect photoelectric properties of the emitters by enhancing the intramolecular charge transfer (ICT) effect and enlarge conjugation with the BP group. Hence, both emitters have high PLQY values (83% and 92%, respectively) in doped films and possess simultaneously small ΔEST values (0.04 and 0.02 eV, respectively). As a result, both 3DMAC-BP-Br and 3DMAC-BP-CN show superior device performance. Especially, DMAC-BP-CN based OLED exhibits a maximum external quantum efficiency (EQE) of 22.43% and low turn-on voltage of 2.8 V.

White organic light-emitting diodes (WOLEDs) with thermally activated delayed fluorescence-sensitized fluorescence (TSF) have aroused wide attention, considering their potential for attaining ultimate high efficiency and long lifetime with pure organic fluorescent emitters. To develop high-performance TSF-based WOLEDs, an efficient energy transfer system is built by combining a conventional host, a stable blue delayed fluorescence sensitizer, and an orange fluorescent dopant in a single-emissive-layer. Transient photoluminescence measurements decipher the Forster resonance energy transfer process with the high exciton utilization and the suppressed Dexter energy transfer in the single-emissive-layer. The TSF-based WOLEDs achieve a maximum external quantum efficiency of 20.9% and the balanced white emission with color coordinates of (0.31, 0.41) because of the partial energy transfer from blue sensitizer to the fluorescent dopant. Moreover, the TSF-WOLEDs exhibit a half-lifetime of ~2,800 h at an initial brightness of 1,000 cd m −2, which can be further improved to >12,000 h by implementing the stacked structure and light outcoupling enhancement techniques. The prolonged device stability is because the TSF system can effectively prevent exciton leakage and suppress the accumulation-caused exciton-annihilation.

Tremendous achievements of colloidal quantum-dot (QD) light-emitting diodes (QLEDs) in both efficiency and lifetime have been witnessed in the past decade. However, multiple interfacial losses such as defect-induced exciton quenching and multicarrier Auger recombination can severely suppress the device performance of QLEDs. Here, we present the efficient QLEDs by adopting the new liquid-solid-solution processed magnesium-doped zinc oxide nanocrystals (ZMO-LSS) as an electron-transport layer. A magic carrier relaxation dynamics is demonstrated at the QD emitter/ZMO-LSS interface for abnormal exciton recycling and enhanced radiative recombination, which arises from the subtle intragap band coupling of surface trap states as directly clarified by the prolonged electroluminescence decays of devices. Red-emitting QLEDs on rigid glass achieve a maximum external quantum efficiency (EQE) of 22.3% with virtual droop-free over a wide range of brightness from 10,000 to 200,000 cd m−2. By further combining a silver nanowires-based composited electrode on a plastic substrate, a substantial boost in EQE up to 24.0% is realized for flexible devices. The present results provide an in-depth study on interfacial recombination and convey a clear picture of constructing ZMO-LSS for efficient QLEDs and related optoelectronic devices.

Two highly efficient thermally activated delayed fluorescent (TADF) materials with twisted donor-acceptor-donor (D-A-D) structure, DMACBB and PXZBB, have been designed and synthesized based on bis(phenylsulfonyl)benzene as the acceptor (A) and 9,9-dimethyl-9,10-dihydroacridine (DMAC) or phenoxazine (PXZ) as the donor (D). Attaching the donor to the 3, 3′-positions of bis(phenylsulfonyl)benzene obtains larger torsion angle between donor and acceptor as well as suitable ICT effects, which results in almost complete separation of their FMOs and limited overlap. Both emitters successfully achieve small ΔEST (≤0.2 eV), simultaneously exhibit high photoluminescence quantum yields (≥80%). Both of them possess distinct TADF features. The DMACBB-based device exhibits sky blue emission with the peak at 472 nm, while the PXZBB-based device shows slightly red-shifted and emits green light with the peak at 507 nm because of the stronger electron-donating ability of PXZ than that of DMAC. The TADF-OLED based on DMACBB achieves higher the maximum external quantum efficiency (EQEmax of 10.1%) than the TADF-OLED based on PXZBB (EQEmax of 8.2%) with the turn-on voltage of 3.5 V.

We have constructed a new approach to realize the light extraction enhancement in organic light-emitting diodes (OLEDs) by using Fe3O4@Au nanoparticles (FOA NPs). The current efficiency of 97.8 cd/A at a luminance of 500 cd/m2 can be obtained for the FOA-NP-based device, while it is only 61 cd/A for the control device without FOA NPs, corresponding a 60% enhancement in efficiency. The time-resolved photoluminescence and optical haze characterizations were performed to study the influence of FOA NPs on the lifetime of excitons and the light-scattering effect, respectively. These results reveal that the enhanced radical efficiency of an FOA-NP-based device is mainly ascribed to the localized surface plasmonic effects induced by Au NPs and the strong light-scattering effect related to FOA NPs, thereby achieving a double enhancement in light extraction, which paves a new way in realizing high-efficiency and controllable OLEDs.

Two novel thermally activated delayed fluorescence (TADF) emitters, 3-phenylquinolino[3,2,1- de]acridine-5,9-dione (3-PhQAD) and 7-phenylquinolino[3,2,1- de]acridine-5,9-dione (7-PhQAD), were designed and synthesized based on a rigid quinolino[3,2,1- de]acridine-5,9-dione (QAD) framework. With the effective superimposed resonance effect from electron-deficient carbonyls and electron-rich nitrogen atom, both emitters realize significant TADF characteristics with small Δ ESTs of 0.18 and 0.19 eV, respectively. And, molecular relaxations were dramatically suppressed for both emitters because of their conjugated structure. In the devices, 3-PhQAD realizes superior performance with a maximum external quantum efficiency (EQE) of 19.1% and a narrow full width at half-maximum (FWHM) of 44 nm, whereas a maximum EQE of 18.7% and an extremely narrow FWHM of 34 nm are realized for 7-PhQAD. These superior results reveal that apart from nitrogen and boron-aromatic systems, QAD framework can also act as a TADF matrix with effective resonance effect, and QAD derivatives are ideal candidates to develop TADF emitters with narrow FWHMs for practical applications.

Perovskite light-emitting diodes (PeLEDs) show great application potential in high-quality flat-panel displays and solid-state lighting due to their steadily improved efficiency, tunable colors, narrow emission peak, and easy solution-processing capability. However, because of high optical confinement and nonradiative charge recombination during electron-photon conversion, the highest reported efficiency of PeLEDs remains far behind that of their conventional counterparts, such as inorganic LEDs, organic LEDs, and quantum-dot LEDs. Here a facile route is demonstrated by adopting bioinspired moth-eye nanostructures at the front electrode/perovskite interface to enhance the outcoupling efficiency of waveguided light in PeLEDs. As a result, the maximum external quantum efficiency and current efficiency of the modified cesium lead bromide (CsPbBr3 ) green-emitting PeLEDs are improved to 20.3% and 61.9 cd A-1 , while retaining spectral and angular independence. Further reducing light loss in the substrate mode using a half-ball lens, efficiencies of 28.2% and 88.7 cd A-1 are achieved, which represent the highest values reported to date for PeLEDs. These results represent a substantial step toward achieving practical applications of PeLEDs.

Flexible organic light-emitting diodes (OLEDs) hold great promise for future bendable display and curved lighting applications. One key challenge of high-performance flexible OLEDs is to develop new flexible transparent conductive electrodes with superior mechanical, electrical, and optical properties. Herein, an effective nanostructured metal/dielectric composite electrode on a plastic substrate is reported by combining a quasi-random outcoupling structure for broadband and angle-independent light outcoupling of white emission with an ultrathin metal alloy film for optimum optical transparency, electrical conduction, and mechanical flexibility. The microcavity effect and surface plasmonic loss can be remarkably reduced in white flexible OLEDs, resulting in a substantial increase in the external quantum efficiency and power efficiency to 47.2% and 112.4 lm W(-1).

Solution-processable metal halide perovskites materials have many advantages, such as adjustable band gap, high photoluminescence quantum yield (PLQY), high color purity, high carrier mobility, low temperature solution process, excellent charge transport property and so on. These make them potential application in the display field. In the past few years, the device performance of perovskite light emitting devices (PeLEDs) have been greatly improved by manipulating the perovskite microstructures through various strategies, such as stoichiometry control, dimensional engineering, defect passivation and so on. At present, except for blue PeLEDs, the external quantum efficiencies (EQEs) over 20% have been achieved for green, red, and near-infrared PeLEDs. The low efficiency of blue PeLEDs is retarding their potential applications in full-color display and solid-state lighting. The main reasons in blue PeLEDs are the poor film coverage of blue perovskite materials and the spectral instability during device operation. In order to improve the quality of perovskite film and device performance, the quasi two-dimensional perovskite materials phenylethylammonium cesium lead bromide chloride (PEAxCsPbBr3–yCly) are used as the main perovskite emission material, by partially replacing Br with Cl to enlarge their bandgap to achieve the blue emission. The Lewis base polyethyleneglycol (PEG) is introduced to passivate the surface trapping defects and improve perovskite film coverage. The potassium bromide (KBr) is introduced to reduce perovskite grain size, suppress mobile ion migration and exhibit excellent spectral stability. Dual additives PEG and KBr are incorporated into the quasi-2D blue perovskite for inhibiting the nonradiative losses by passivating the traps in the perovskite films. Eventually, the PEAxCsPbBr3–yCly + PEG + KBr based blue PeLEDs with the emission peak of 488 nm are accompanied, which maximum brightness, current efficiency, and external quantum efficiency reached 1049 cd·m–2, of 5.68 cd·A–1, and of 4.6%, respectively, with high color purity (the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates is (0.0747, 0.2570)) and the narrow full width at half maximum (FWHM) of 20 nm. Compare to the devices without additives, the efficiency has increased by nearly 3 times. Furthermore, the devices also show better spectral stability and operation lifetime. This work provides an effective method of blue PeLEDs toward the practical applications.

Flexible organic light-emitting diodes are gaining increasing importance as a leading technology for high-quality displays and lighting in wearable electronics due to their low power consumption, excellent color gamut, and the desirable mechanical flexibility with soft materials and curvilinear surfaces. However, further enhancements in efficiency are still challenging because of the optical confinement and limited light out-coupling efficiency. Here, a simple and wavelength-independent light extraction scheme is demonstrated using the biomimetic quasirandom nanostructures that can simultaneously enhance the out-coupling of the waveguided light and allow the minimized ohmic losses without spectral distortion. Compared to periodic grating structures, the nanoimprinted quasirandom nanostructures can broaden the periodicity and randomize the emission directionality, leading to the superiority of color stability over the visible wavelength range for a large variation of viewing angles. The resulting external quantum efficiency and current efficiency are 1.51 and 1.43 times that of a conventional flexible organic light-emitting diode used as a comparison, respectively.

Highly power-efficient white organic light-emitting diodes (OLEDs) are still challenging to make for applications in high-quality displays and general lighting due to optical confinement and energy loss during electron-photon conversion. Here, an efficient white OLED structure is shown that combines deterministic aperiodic nanostructures for broadband quasi-omnidirectional light extraction and a multilayer energy cascade structure for energy-efficient photon generation. The external quantum efficiency and power efficiency are raised to 54.6% and 123.4 lm W−1 at 1000 cd m−2. An extremely small roll-off in efficiency at high luminance is also obtained, yielding a striking value of 106.5 lm W−1 at 5000 cd m−2. In addition to a substantial increase in efficiency, this device structure simultaneously offers the superiority of angular color stability over the visible wavelength range compared to conventional OLEDs. It is anticipated that these findings could open up new opportunities to promote white OLEDs for commercial applications.

Inverted organic light-emitting diode (OLED) has attracted extensive attention due to the demand in active-matrix OLED display panels as its geometry enables the direct connection with n-channel transistor backplane on the substrate. One key challenge of high-performance inverted OLED is an efficient electron-injection layer with superior electrical and optical properties to match the indium tin oxide cathode on substrate. We here propose a synergistic electron-injection architecture using surface modification of ZnO layer to simultaneously promote electron injection into organic emitter and enhance out-coupling of waveguided light. An efficient inverted white OLED is realized by introducing the nanoimprinted aperiodic nanostructure of ZnO for broadband and angle-independent light out-coupling and inserting an n-type doped interlayer for energy level tuning and injection barrier lowering. As a result, the optimized inverted white OLEDs have an external quantum efficiency of 42.4% and a power efficiency of 85.4 lm W

Flexible organic light-emitting diodes (OLEDs) are emerging as a leading technology for rollable and foldable display applications. For the development of high-performance flexible OLEDs on plastic substrate, we report a transparent nanocomposite electrode with superior mechanical, electrical, and optical properties, which is realized by integrating the nanoimprinted quasi-random photonic structures into the ultrathin metal/dielectric stack to collectively optimize the electrical conduction and light outcoupling capabilities. The resulting flexible OLEDs with green emission yield the enhanced device efficiency, reaching the maximum external quantum efficiency of 43.7% and luminous efficiency of 154.9 cd/A, respectively.

Rapid progress in the power conversion efficiency (PCE) of polymer solar cells (PSEs) is beneficial from the factors that match the irradiated solar spectrum, maximize incident light absorption, and reduce photogenerated charge recombination. To optimize the device efficiency, a nanopatterned ZnO:Al2 O3 composite film is presented as an efficient light- and charge-manipulation layer (LCML). The Al2 O3 shells on the ZnO nanoparticles offer the passivation effect that allows optimal electron collection by suppressing charge-recombination loss. Both the increased refractive index and the patterned deterministic aperiodic nanostructure in the ZnO:Al2 O3 LCML cause broadband light harvesting. Highly efficient single-junction PSCs for different binary blends are obtained with a peak external quantum efficiency of up to 90%, showing certified PCEs of 9.69% and 13.03% for a fullerene blend of PTB7:PC71 BM and a nonfullerene blend, FTAZ:IDIC, respectively. Because of the substantial increase in efficiency, this method unlocks the full potential of the ZnO:Al2 O3 LCML toward future photovoltaic applications.

To realize high-efficiency organic light-emitting diodes (OLEDs), it is essential to boost out-coupling efficiency. Here we review our latest reports upon light manipulation for OLEDs by integrating a dual-side bio-inspired deterministic quasi-periodic moth’s eye nanostructure with broadband anti-reflective and quasi-omnidirectional properties. Light out-coupling efficiency of OLEDs with stacked triple emission units is over 2 times that of a conventional device, resulting in drastic increase in external quantum efficiency and current efficiency to 119.7% and 366 cd A-1 without introducing spectral distortion and directionality. Theoretical calculations furthermore clarify that the improved device performance is primarily attributed to the effective extraction of the waveguide and surface plasmonic modes of the confined light over all the emission wavelengths and viewing-angles.

We demonstrated an efficient inverted CdSe/CdS/ZnS quantum dot light emitting diode (QLED) using sol-gel ZnO (s-ZnO) as the electron-injection layer (EIL). The device performance is comparable to that of a device based on the common used nanoparticle ZnO (n-ZnO) EIL. The peak efficiency (12.5 cd/A) and luminance (13000 cd/m2) for the s-ZnO based device was found to be similar to the n-ZnO based device (11.2 cd/A and 15000 cd/m2). The morphology properties of these two types of ZnO films were investigated by scanning electron microscope (SEM) and atomic force microscope (AFM) measurements. A very smooth surface was achieved for the s-ZnO film. Moreover, the quantum dot (QD) layer on the s-ZnO also possesses high quality with a close packed structure.

Organic-based optoelectronic devices, including light-emitting diodes (OLEDs) and solar cells (OSCs) hold great promise as low-cost and large-area electro-optical devices and renewable energy sources. However, further improvement in efficiency remains a daunting challenge due to limited light extraction or absorption in conventional device architectures. Here we report a universal method of optical manipulation of light by integrating a dual-side bio-inspired moth's eye nanostructure with broadband anti-reflective and quasi-omnidirectional properties. Light out-coupling efficiency of OLEDs with stacked triple emission units is over 2 times that of a conventional device, resulting in drastic increase in external quantum efficiency and current efficiency to 119.7% and 366 cd A(-1) without introducing spectral distortion and directionality. Similarly, the light in-coupling efficiency of OSCs is increased 20%, yielding an enhanced power conversion efficiency of 9.33%. We anticipate this method would offer a convenient and scalable way for inexpensive and high-efficiency organic optoelectronic designs.

An organic light-emitting device (OLED) having a double-heterostructure of ITO/NPB/DCMdoped Alq3/BCP/Alq3/MgAg was constructed to form a narrow recombination zone where both charge carriers and excitons are confined, thus resulting in efficient electron-hole recombination and energy transfer. It was found that though luminance efficiency was enhanced, the low electron mobility of BCP resulted in higher driving voltages and limited the improvement of power efficiency. Significant improvements on both quantum efficiency and power efficiency were achieved by replace 1,3,5-tri(phenyl-2-benzimidazoly)-benzene (TPBI) for BCP, and were correlated with its high electron mobility. Device performance was further improved in the structure ITO/NPB/DCM-doped Alq3/TPBI/LiF/MgAg with a maximum luminance efficiency 6.03cd/A and a power efficiency of 5.94 lm/W.

SiN-based multilayers were prepared in a plasma enhanced chemical vapor deposition system followed by subsequently thermal annealing and laser irradiation with the aim of fabrication three-dimensional constrained, size-controlled and well-regulated Si nanocrystals. The experimental results show that Si nanocrystals grow in the Si-rich SiN sublayer. Furthermore, the grain size can be controlled according to the thick of Si-rich SiN. It is also found that the crystalline fraction of the multilayers irradiated by laser is significantly higher than that by thermal annealing. The devices that employing the laser-irradiated multilayer as luminescent active layer exhibit an enhanced visible electroluminescence and the external quantum efficiency is improved by 40% in comparison with the device without annealing.