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Photodiode‐type solar‐blind photodetectors (SBPDs) with the self‐powered feature hold great promise for applications in unattended secure communication, flame detection, and missile warning. However, the responsivity of SBPDs is usually limited due to the severe solar‐blind (SB) light extinction in substrates and charge transport layers. Herein, a spectrally selective hole extraction structure (SHE) is proposed for high‐efficiency perovskite SBPDs. The SHE consisting of a tandem Fabry–Perot cavity and energy‐level‐matched hole transport layer endows the device with narrowband absorption in the SB region and optimized charge extraction capability from the CsPbI2Br perovskite. The optimized SHE exhibits a peak transmittance of 27% at 255 nm and a half maximum at full width of 28 nm. Under SB light illumination, the champion device achieves a responsivity of 56.20 mA W−1 and a detectivity (D*) of 2.86 × 1013 Jones, which are the record values among the reported results. The approach demonstrated here paves the way for the optical and electrical design of perovskite photodetectors with spectrally selective detection. [ABSTRACT FROM AUTHOR]

Semitransparent organic solar cells (STOSCs) hold great promise for applications ranging from building‐integrated photovoltaics to portable electronic devices, yet often challenging over the realization of color tunability. The structural colors generated by microcavity, subwavelength grating, or photonic crystals are highly dependent on the viewing angle, which limits the application of STOSCs in real scenarios. Herein, the spectrally selective substrates consisting of silica spheres‐based amorphous photonic crystals (APCs) are proposed to unify the optical spectra of STOSCs at different viewing angles. By optimizing the periodicity of APCs, STOSCs exhibit viewing‐angle‐independent reflection with colors varying from blue to pink. The synergetic interplay between the reflection of APCs and the absorption of active layer results in the Janus optical effect that the transmitted light is fixed at blue regardless of the reflected color. The STOSCs on flexible plastic retain the stable color even at bending state. These results pave the way for the potential application of colorful solar photovoltaic glass curtains. [ABSTRACT FROM AUTHOR]

White organic light‐emitting diodes (WOLEDs) based on thermally activated delayed fluorescence (TADF) emitters attract considerable attention owing to the advantages of full exciton harvesting, low cost, and environmental sustainability. However, compared to phosphorescent counterparts, the power efficiencies of TADF‐based WOLEDs lag behind. Herein, a newly synthesized TADF emitter named DPPZ‐DMAC featuring near‐zero singlet−triplet splitting and high photoluminescence quantum yield (91.6%) is utilized as an ideal orange‐yellow dopant for realizing a power‐efficient WOLED with a mixed system consisting of a blue TADF sensitizer and a conventional fluorescent host. The balanced carrier transport, modulated energy transfer and exciton harvesting, and less exciton quenching can be realized simultaneously. Eventually, a warm WOLED is achieved with an external quantum efficiency of ≈30%, power efficiency of >80 lm W‐1, turn‐on voltage of 2.5 V, and correlated color temperature of 3600 K. Moreover, the color coordinate of the resulting white emission is close to the standard blackbody radiation and can be precisely tuned inside the specific quadrangles given by the American National Standard Institute (ANSI), revealing a large prospect for indoor health lightings. [ABSTRACT FROM AUTHOR]

Circularly polarized organic light‐emitting diodes (CP‐OLEDs) that enable circularly polarized luminescence (CPL) are promising for 3D display and photonic applications. However, the device efficiency and CPL character of CP‐OLEDs still lag behind the practical requirements. Here, two pairs of axially chiral emitting enantiomers, flexible (R/S)‐ODQPXZ and rigid (R/S)‐ODPPXZ, are reported by fusing (R/S)‐octahydro‐binaphthol chiral source, diphenyl quinoxaline (DQ)/dibenzo[a,c]phenazine (DP) acceptors and phenoxazine (PXZ) donors. The symmetrical chiral‐acceptor‐donor configuration endows them thermally activated delayed fluorescence (TADF) properties with small singlet–triplet energy gaps of 0.16 and 0.07 eV, high photoluminescence quantum yields of 92% and 89% in doped films, and obvious mirror‐image CPL characteristics, respectively. The CP‐OLEDs based on these TADF enantiomers not only show a maximum external quantum efficiency of 28.3% with yellow emission for (R/S)‐ODQPXZ and 20.3% with orange‐red emission for (R/S)‐ODPPXZ, but also display the CPL with dissymmetry factors (gEL) of 6.0 × 10−4 and 2.4 × 10−3, respectively. The high efficiency and obvious CPL of (R)‐ODPPXZ arise from a synergetic interplay of the TADF skeleton and the rigid coplanar acceptor for efficient chiral induction and suppressed intramolecular rotational quenching. [ABSTRACT FROM AUTHOR]

Flexible organic solar cells (OSCs) are very promising for use in portable power supply devices due to the advantages of low‐cost, light‐weight, and flexibility. However, the efficiencies of flexible OSCs are limited by the flexible transparent electrodes owing to their nonoptimal electrical, optical, and mechanical properties. To address these challenges, leaf‐like biomimetic electrodes are proposed to achieve an efficient light capture and glossy surface for a high‐efficiency flexible OSC. To mimic the internal anatomy of the leaf, the conformable electrode stack consists of a flexible polyimide substrate, light‐scattering polystyrene spheres, zinc oxide protecting layer, and electrically conductive silver nanowires to obtain a high transmittance, low sheet resistance, and low surface roughness. A record‐high power conversion efficiency of 16.1% is realized by a flexible OSC with the biomimetic electrode design, comparable to those rigid devices on glass. Moreover, the flexible OSC on this biomimetic electrode exhibits a robust bendability against flexural strain, retaining 85% of the initial efficiency after 5000 bending cycles at a radius of curvature as small as 1.0 mm. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An efficient tandem organic light‐emitting diode is realized by employing a novel light out‐coupling structure with deterministic quasi‐periodic nanocone arrays. The enhancement of color spatial uniformity and operational stability is simultaneously realized along with the remarkable efficiency improvement in tandem devices by integrating multi‐photon emission and light out‐coupling techniques. The optimized tandem organic light‐emitting diode with two emission units exhibits an enhancement factor of 4.99 and 10.49 for device efficiency and half‐decay lifetime, respectively, as compared to the conventional device with a planar single‐unit structure. Moreover, it is verified that the emission color with viewing angles was significantly stabilized with no apparent spectral distortion. Theoretical calculations 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. [ABSTRACT FROM AUTHOR]

Flexible organic light‐emitting diodes (OLEDs) are attracting tremendous attention due to their promise as a key element in bendable display and curved lighting applications. However, their performance in terms of efficiency and bendability is limited, since flexible transparent electrodes with superior electrical, optical, and mechanical properties are rare. Here, a multifunctional electrode architecture that is based on flexible plastic, and consists of electrically conductive silver nanowires, a nanopatterned ZnO outcoupling layer, and a hole‐injection polymer layer, is proposed for the actualization of high‐performance flexible OLEDs. The trapped light in the waveguide and substrate modes is effectively released by integrating aperiodic nanostructures into high‐refractive‐index ZnO layers on both sides of the plastic substrate. A maximum external quantum efficiency of 61.7% and a power efficiency of 126.6 lm W−1 are achieved for the white‐emission flexible OLEDs with broadband and angle‐independent outcoupling enhancement. In addition, the proposed approach allows for high‐level mechanical flexibility, retaining over 80% of the initial efficiency after 3000 cycles of repeated bending. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells (PeSCs) possess the extraordinary potential in the applications of portable power sources and wearable electronics because of their superiorities in ease fabrication and efficient power conversion. These features are reinforced when a transparent conductive electrode with good flexibility is achieved. A unique electrode based on Ag periodic mesh (APM) perforated with hexagonal close‐packed nanoholes is proposed, showing a square resistance of ≈19.0 Ω sq−1 and optical transmittance of 66.0% in the whole visible region. PeSCs made on the optimal APM electrode with a rigid glass substrate achieve over twofold of photocurrent as compared to the counterpart on flat Ag film, resulting in a maximum power conversion efficiency of 17.06%. Experimental and theoretical characterizations indicate that the performance enhancement is mainly ascribed to the surface plasmon‐assisted extraordinary transmission enhancement and the scattering of incident light. Furthermore, the APM electrode enables PeSCs that are not only efficient but also highly flexible against bending deformation. Flexible PeSCs on plastic remain 90% of their initial efficiency after 1500 bending cycles with a bending radius of 3.0 mm. It is anticipated that the APM electrode with unique light coupling abilities provides a facile design route to achieving efficient and flexible PeSCs. [ABSTRACT FROM AUTHOR]

In article number 1801534, Yan‐Qing Li, Feng Gao, Chun‐Sing Lee, Jian‐Xin Tang, and co‐workers propose a method for the synergetic morphology control over cesium lead bromide perovskite films. Bright perovskite light‐emitting diodes (PeLEDs) are achieved due to the synergetic interplay of small grain sizes for efficient energy funneling and defect passivation for suppressing nonradiative recombination losses. Efficient flexible PeLEDs on plastics are also realized, showing great potential for commercially viable applications. [ABSTRACT FROM AUTHOR]

Light manipulation strategy plays a critical role in increasing the light harvesting of organic solar cells (OSCs). However, the incorporation of light manipulation structures in OSCs is usually hindered by complex lithography‐based techniques. Herein, a facile and solution‐processed structured ZnO film is proposed, consisting of ZnO colloidal spheres (CS) embedded in ZnO nanoparticles for broadband light scattering and antireflection in OSCs. By combining monodisperse ZnO CS (m‐ZnO) as an electron collection layer and polydisperse ZnO CS (p‐ZnO) as an antireflection layer, single‐junction OSCs yield a substantial increase in photocurrent and power conversion efficiency by 14.63% compared to the reference cell with a flat structure. The experimental and theoretical characterizations ascribe the performance enhancement to the enhanced absorption due to a synergetic interplay of p‐ZnO‐induced antireflection and surface plasmonic scattering excited by corrugated metal electrode. It is anticipated that this light manipulation method represents a facile yet cost‐effective route to achieving high‐efficiency OSCs for commercially viable photovoltaic applications. A facile, solution‐processed light manipulation scheme consisting of ZnO colloidal spheres and nanoparticles is proposed for achieving high‐efficiency organic solar cells. The light harvesting enhancement by 14.63% is obtained by a synergetic interplay of broadband light scattering, surface plasmonic resonance, and the antireflective effect due to the structured ZnO films. [ABSTRACT FROM AUTHOR]

In article number 1801292, Yan‐Qing Li, Jian‐Xin Tang and co‐workers demonstrate a facile and solution‐processed light manipulation scheme consisting of ZnO colloidal spheres and nanoparticles for achieving highly efficient organic solar cells. The enhanced device performance benefits from the concentrated electromagnetic field in the absorber with the coupling of anti‐reflection effect, light scattering effect and localized surface plasmon resonance. [ABSTRACT FROM AUTHOR]

In article number 1801153, Yan‐Qing Li, Jian‐Xin Tang and co‐workers demonstrate a facile route to achieving indium‐free flexible perovskite solar cells with high efficiency and superior repeated bendability. The performance enhancement benefits from the synergetic interplay of a composite electrode stack, consisting of an electrically conductive silver nanowires network, a sol–gel‐derived ZnO smoothing layer, and an atomic‐layer‐deposited TiO2 passivation layer. This device architecture shows potential for the low‐cost roll‐to‐roll processing of flexible perovskite devices. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells (PeSCs) hold great potential as a leading technology for large‐scale roll‐to‐roll production of highly efficient renewable energy sources. To achieve long‐term bendability and competitive photovoltaic properties for flexible PeSCs, an efficient strategy is reported for a fully indium‐free flexible composite electrode, consisting of solution‐processed silver nanowires (AgNWs) conductive network, a sol–gel‐derived ZnO protective layer for smoothing the surface, and an atomic‐layer‐deposited TiO2 passivation layer for eliminating the perovskite decomposition. The synergetic interplay of this electrode stack results in good electrical conductivity, optical transparency, mechanical robustness, and low‐temperature processability. With collective optimization of this composite electrode, flexible PeSCs on plastics realize a power conversion efficiency of 17.11%, which is comparable to that of conventional indium‐tin‐oxide‐based device (18.26%). Moreover, flexible PeSCs using this composite electrode are repeatedly bendable, retaining 77% of their initial efficiency after 2000 bending cycles at a radius of 6 mm. Because of the ease of use and remarkable improvement in efficiency, this flexible composite electrode will help to enable the low‐cost roll‐to‐roll processing of flexible PeSCs. A facile route to achieve flexible perovskite solar cells with an efficiency of 17.11% is proposed, which benefits from the synergetic interplay among electrically conductive silver nanowires network, sol–gel‐derived ZnO protective layer, and ultrathin atomic layer deposition‐assisted TiO2 passivation layer. These flexible devices are repeatedly bendable due to excellent flexural strain resistance. [ABSTRACT FROM AUTHOR]

Transparent flexible organic light‐emitting diodes (TF‐OLEDs) are emerging as a leading technique in bendable display and curved lighting applications due to their merits including superior mechanical flexibility, low power consumption, and broad color gamut. However, it is challenging to turn TF‐OLEDs into a power‐efficient large‐area light source. Here, an improved TF‐OLED structure on a plastic substrate that achieves a device transparency over 70% and extremely efficient warm‐white emission from both sides is reported. The key feature of this device structure is the combination of transparent metal–dielectric composite electrodes, which are patterned with moth‐eye nanostructures for broadband and angle‐independent light outcoupling. By collectively reducing ohmic losses and releasing the trapped photons, the TF‐OLEDs achieve a record external quantum efficiency of 72.4% and power efficiency of 168.5 lm W−1 with a color‐rendering index over 84. These results present the great potential of TF‐OLEDs for use in a wide variety of flexible applications. By taking a full advantage of the optical design, an extremely efficient transparent flexible organic light‐emitting diode achieves a record external quantum efficiency of 72.4% and power efficiency of 168.5 lm W−1 for white emission with a color‐rendering‐index of 84.5. The substantial increase in efficiency is due to the synergetic interplay of light outcoupling enhancement and minimized surface plasmon losses. [ABSTRACT FROM AUTHOR]

Near ultraviolet (NUV) organic light‐emitting diodes (OLEDs) have great advantages in the field of light excitation sources, chemical and biological sensors, etc. However, the molecular design of NUV emitters still faces the challenges of spectral broadening and red‐shift. In this study, attaching weak oxygen‐bridged triarylboron acceptor to weak carbazolyl donor is able to address intractable problems by weakening donor–acceptor (D–A) charge transfer. Simultaneously, sterically wrapped and modified oxygen‐bridged triarylboron acceptor by bulk substituents (multiple carbazolyl) can suppress intermolecular π–π stacking through steric hindrance effect. These design strategies are able to obtain short‐wavelength, narrow‐band emission, and great color purity. As a result, carbazolyl derivatives xCz‐BO‐based (x = 2, 3, 4, 5) emitters show EL emission peaks from 406 to 422 nm in the NUV light region and small full‐width at half‐maximums (FWHMs) of 32–41 nm over a wide range of dopant concentrations (10–40 wt.%). The most violet Commission International de I'Eclairage (CIE) color coordinate is (0.16, 0.03). Moreover, 5Cz‐BO can be employed as host for vacuum‐/solution‐processed blue OLEDs and these devices exhibit high performance with EQEs of over 20%. [ABSTRACT FROM AUTHOR]