ABSTRACT All‐polymer solar cells lag behind state‐of‐the‐art small‐molecule non‐fullerene acceptor (NFA)‐based bulk heterojunction (BHJ) organic solar cells (OSCs) in terms of power conversion efficiency. Here, the efficiency‐limiting processes in all‐polymer solar cells using blends of the donor polymer PBDB‐T or PBDB‐T‐2F (PM6) and either of two recently developed acceptor polymers, coded PYN‐BDT and PYN‐BDTF, are investigated. The acceptor polymers exhibit strong light absorption up to 900 nm due to π‐extended naphthalene moieties. Combining results from steady‐state optical spectroscopies, as well as time‐resolved photoluminescence, transient absorption, photoluminescence detected magnetic resonance, and time‐delayed collection field experiments, provides a concise and quantitative evaluation of loss channels. Kinetic parameters and process yields obtained by pulsed laser spectroscopy are shown to reproduce the experimentally measured device current‐voltage characteristics, indicating that the moderate fill factors are caused by non‐geminate recombination competing with charge extraction, as well as field‐dependent charge generation, the impact of either changing with the acceptor polymer. The methodology described here is generally applicable to quantify loss processes in BHJ OSCs, not only in all‐polymer, but also in small‐molecule NFA systems.

Designing small-molecule acceptors (SMAs) with long exciton diffusion length (LD) and high electron mobility is vital for boosting power conversion efficiency (PCE) of organic solar cells (OSCs). However, the limited LD of most advanced SMAs hinders their practical applications in thick-film OSCs. Herein, we develop four SMAs (named Yq-0F, Yq-2F, Yq-4F, and Yq-6F) with fluorine-free/fluorinated phenyl-substituted quinoxaline cores by manipulating the number of fluorine atom. Among them, polyfluorophenyl-substituted Yq-4F exhibits superior 3D network crystal framework and favourable intermolecular packing, leading to optimal blend morphology with polymer donor D18. Therefore, D18:Yq-4F system achieves improved carrier mobilities and suppressed charge recombination loss. Consequently, the D18:Yq-4F based binary OSCs provide a PCE of 18.30%, surpassing these ones based on D18:Yq-0F (11.27%), D18:Yq-2F (17.73%), and D18:Yq-6F (17.00%). When introducing Yq-4F as a guest into D18:L8-BO host to fabricate ternary OSCs, the PCE further increases to 20.77%, as the highest reported value among quinoxaline-derived SMAs. Moreover, ternary D18:Yq-4F:BTP-eC9 and D18:L8-BO:Yq-4F OSCs with ~500 nm active layer thickness offer impressive PCEs of >17%, ranking among the top values for thick-film devices with similar thickness. This work offers an effective SMA design strategy for opening a path towards efficient thin-film and thick-film OSCs simultaneously.

ABSTRACT Ruthenium oxide (RuO 2 ) is a promising alternative to Ir‐based catalysts for the acidic oxygen evolution reaction (OER) owing to its high intrinsic activity, yet its practical application is hindered by rapid degradation under strongly oxidative acidic conditions. Herein, we report a dual rare‐earth co‐doping strategy to regulate Ru─O bonding through the synergistic coupling of strain and electronic effects. Incorporation of lanthanum (La) and neodymium (Nd) into the rutile RuO 2 lattice induces a 2.41% lattice expansion, resulting in elongated Ru─O bonds and weakened Ru─O covalency. These structural modifications suppress lattice oxygen activation and stabilize the oxide framework. Meanwhile, rare‐earth‐induced electronic modulation lowers the energy barrier for the *O to *OOH transition, steering OER toward a more stable adsorbate evolution mechanism (AEM) pathway. Consequently, LaNd‐RuO 2 achieves an overpotential of only 185 mV at 10 mA cm −2 in 0.5 M H 2 SO 4 and sustains stable operation for over 1200 h, significantly outperforming singly doped counterparts. A proton exchange membrane water electrolyzer employing LaNd‐RuO 2 as the anode catalyst requires only 1.81 V to reach 3 A cm −2 . This work offers an effective strategy for simultaneously enhancing the activity and durability of Ru‐based acidic OER catalysts.

The typical design strategy for non-conjugated polymer acceptors involves the alternating distribution of small molecule acceptor units and non-conjugated units along the main chain. In this study, we proposed a novel design strategy for non-conjugated polymer acceptors and synthesized a non-conjugated polymer acceptor (SPA-1) incorporating grafted A-DA'D-A type small molecule units within its side chain. The binary all-polymer solar cells (All-PSCs) based on PBDB-T:SPA-1 showed a power conversion efficiency (PCE) of 11.16%, and the ternary All-PSCs based on PM6:PY-IT:SPA-1 achieved a PCE of 17.91%.

Chiral single molecules that exhibit both thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) pose significant challenges, primarily due to their competitive luminescence mechanisms and the scarcity of studies on their applications in circularly polarized organic light-emitting diodes (CP-OLEDs). In this work, we develop a novel chiral emitter, CP-D3, with an axially chiral biphenyl segment selected as the chiral center. As a result, CP-D3 successfully exhibits both TADF and RTP properties with a high photoluminescence (PL) efficiency of 91%. The high dissymmetry factors (g(CPPL)) of -7.98 x 10(-3) and +7.47 x 10(-3) are obtained for (R/S)-CP-D3, respectively. Notably, the CP-D3-based CP-OLEDs achieve a maximum external quantum efficiency (EQE(max)) of 32.44%, which represents the highest value among chiral luminance materials based on an axially chiral biphenyl component. The g(CPEL) is recorded as -8.13 x 10(-4)/+5.92 x 10(-4) for (R/S)-CP-D3-based CP-OLEDs. This work presents the first report on a chiral single-molecule emitter incorporating an axially chiral biphenyl component, which exhibits simultaneous TADF and RTP emissions and enables highly efficient CP-OLEDs.

Organic light-emitting diodes (OLEDs) employing multiple resonance-thermally activated delayed fluorescence (MR-TADF) emitters exhibit high exciton utilization efficiency and outstanding color purity. Nevertheless, typical MR-TADF emitters possessing well-developed conjugated planarity often encounter significant aggregation-induced quenching (ACQ) effect through pi-pi stacking, which substantially impacts device efficiency and color purity. To address these issues, in this work, large steric hindrance groups 4,4 '-bicarbazole derivatives are incorporated into the MR core (BCz-BN) to obtain two target molecules, namely BCz-BNDCzMe and BCz-BNDCzPh. Compared to BCz-BN, which exhibits an electroluminescence (EL) emission peak at 488 nm with a full width at half maximum (FWHM) of 30 nm, BCz-BNDCzMe and BCz-BNDCzPh demonstrate blue-shifted emissions peaking at 481-482 nm and featuring narrower FWHM values of 25-26 nm. Remarkably, the maximum external quantum efficiency (EQEmax) of 26.75-28.31% is achieved for BCz-BNDCzMe and BCz-BNDCzPh based devices at high doping concentrations (10-20 wt.%). These values are significantly higher than the EQEmax of 20.50% for BCz-BN-based devices at a 3 wt.% doping level. These findings unequivocally indicate that incorporating a bulky steric hindrance group into the MR-TADF core efficiently mitigates interchromophore interactions, thereby further suppressing the ACQ effect and enhancing device efficiency at high doping concentrations.

Developing narrow‐bandgap nonfullerene acceptors (NFAs) with high photoluminescence quantum yield (PLQY) is a major challenge, but also a promising strategy to reduce nonradiative energy loss for boosting power‐conversion‐efficiency (PCE) of organic solar cells (OSCs). Herein, we design and synthesize a Y‐series NFA (Y‐NFA, named TQX‐IC) by incorporating a triptycene‐derived “highly luminescent” and “3D‐architectured” substituent. Study shows that TQX‐IC can suppress aggregation‐caused quenching (ACQ), achieving a remarkable PLQY of 12.80%, currently one of the highest reported values among Y‐NFAs. Therefore, its binary OSCs offer an exceptionally low nonradiative energy loss of 0.148 eV, significantly outperforming the control Y‐NFA named Me‐Y (0.209 eV). When incorporating it as a third component into D18:BTP‐eC9 and D18:L8‐BO systems, ternary OSCs based on both D18:BTP‐eC9:TQX‐IC and D18:L8‐BO:TQX‐IC achieve impressive PCEs of 19.48% and 20.26%, respectively, significantly surpassing the Me‐Y based ternary OSCs (18.19% and 18.23%). This enhancement of ternary systems is attributed to the reduced nonradiative energy loss, optimized exciton dynamics, improved charge transport, and optimized active layer morphology and component distribution when compared to their binary systems. Our findings demonstrate that introducing “highly luminescent” and “3D‐architectured” substituent into Y‐NFAs is a promising approach to enhance PLQY, thereby paving the way toward efficient OSCs.

Near-infrared(NIR)responsive compounds with narrow bandgaps play a crucial role in enhancing the photovoltaic effi-ciency of organic solar cells(OSCs)by effectively capturing high-energy NIR photons,as well as improving the NIR sensitiv-ity of organic photodetectors(OPDs)through NIR light detec-tion[1,2].

Multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters have been widely used for highly efficient and ultrapure organic light-emitting diodes (OLEDs) via thermal deposition, while the low-cost solution procedure still remains underexplored. Herein, we propose a TADF polymer as the sensitizer of a narrowband emitter to fabricate solution-processed MR-TADF OLEDs. Due to the effective harvesting of triplet excitons, the sensitized devices based on TADF polymer achieve a narrowband electroluminescence, revealing a maximum external quantum efficiency (EQEmax) of 15.7% together with CIE coordinates of (0.28, 0.65). The performance is approximately 2 times higher than that of non-sensitized devices (7.0%), highlighting the great potential of TADF polymers in efficient solution-processed MR-TADF OLEDs. Solution-processed TADF polymer sensitized MR-TADF OLEDs demonstrate EQE of 15.7% with a narrow FWHM of 48 nm.

D31 and D32 with different connection positions exhibit aggregation-diminished and aggregation-enhanced organic room temperature electrophosphorescence, respectively.

Organic mixed ionic-electronic conductors (OMIECs) play a fundamental role in the performance of organic electrochemical transistors (OECTs) and their applications. Although several depletion mode and accumulation mode OMIECs have been utilized for efficient OECT-based glucose sensors, there are still persistent drawbacks such as including biocompatibility, instability, or high detection limits. In this work, a series of indacenodithiophene-based polymeric OMIECs (gIDT, gIDT-T, and gIDT-DTBT) are developed, where the influences of backbone structure on their optical bandgap, energy level, electrochemical propriety, charge transfer and transistor performance, are systematically investigated. By applying KPF6 electrolyte and vertical device structure, gIDT-DTBT-based vertical OECTs (vOECTs) achieved a maximum output current of -15.63 mA, a maximum transconductance of 39.99 mS, and stable output current (less than similar to 2% decay) over 1000 switching cycles. In addition, such vOECTs are employed to detect glucose concentrations ranging from 0.9 to 22.5 mu M. A low limit of detection (0.1 mu M) and good selectivity are demonstrated. This study indicates that the combination of regulating OMIECs' backbone structure, selecting appropriate electrolytes, and implementing a vertical device structure can help optimize OECT performance and its biosensor applications.

Boron-nitrogen doped multiple resonance (BN-MR) emitters, characterized by B-N covalent bonds, offer distinctive advantages as pivotal building blocks for facile access to novel MR emitters featuring narrowband spectra and high efficiency. However, there remains a scarcity of exploration concerning synthetic methods and structural derivations to expand the library of novel BN-MR emitters. Herein, we present the synthesis of a BN-MR emitter, tCz[B-N]N, through a one-pot borylation reaction directed by the amine group, achieving an impressive yield of 94%. The emitter is decorated by incorporating two 3,6-di-t-butylcarbazole (tCz) units into a B-N covalent bond doped BN-MR parent molecule via para-C-pi-D and para-N-pi-D conjugations. This peripheral decoration strategy enhances the reverse intersystem crossing process and shifts the emission band towards the pure green region, peaking at 526 nm with a narrowband full-width at half maximum (FWHM) of 41 nm. Consequently, organic light emitting diodes (OLEDs) employing this emitter achieved a maximum external quantum efficiency (EQEmax) value of 27.7%, with minimal efficiency roll-off. Even at a practical luminance of 1000 cd center dot m-2, the device maintains a high EQE value of 24.6%.

Chiral organic phosphors with room-temperature phosphorescence (RTP) show a great potential in high-performance circularly polarized organic light-emitting diodes (CP-OLEDs). As a proof of concept, herein, we report a pair of chiral RTP enantiomers (S/R)-CP-RTP-D1 with acridine as the donor (D), triazine as the acceptor (A), oxygen as the bridge, and (S/R)-2-methylbutane as the chiral alkyl chain. It is found that the effective chiral perturbation can endow (S/R)-CP-RTP-D1 with mirror symmetric chiroptical properties, while maintaining the characteristic RTP emission. Consequently, the corresponding doped and non-doped CP-OLEDs based on (S/R)-CP-RTP-D1 achieve obvious circularly polarized electroluminescence (CPEL) signals, revealing promising external quantum efficiencies of 14.9

Polymeric light-emitting diodes (PLEDs) are believed to show promising applications in low-cost and large-area flat-panel displays and solid-state lighting because of the intrinsic solution processability by means of blade coating, screen-printing, inkjet printing, etc. This chapter summarizes the recent developments in solution-processable polymeric emitters used for PLEDs, including fluorescent polymers, metal-containing phosphorescent polymers, and thermally activated delayed fluorescence polymers. Special attention is paid to the relationships between molecular structures and device performance.

Thermally activated delayed fluorescence (TADF) polymers show a great potential in low-cost, large-area and flexible full-color flat-panel displays. One of the most promising design rules is based on TADF+Linker, where a small molecular TADF unit is bonded to each other by a simple linker. Unlike the expensive vacuum deposition for small molecules, these polymerized TADF small molecules (Poly-TADF-SMs) are capable of cost-effective solution processing. Meanwhile, the good luminescent property of small molecular TADF emitters can be well inherited by Poly-TADF-SMs so as to bridge the efficiency gap between small molecules and polymers. Herein, we will highlight the recent progress of Poly-TADF-SMs, together with emphasis on their molecular design, photophysical and electroluminescence properties. Polymerized TADF small molecules capable of cost-effective solution processing are believed to bridge the efficiency gap between small molecules and polymers. And their recent progress is highlighted so as to shed light on the development of efficient TADF polymers. image

AbstractSolution‐processed fluorescent organic light‐emitting diodes (OLEDs) are believed to be favorable for low‐cost, large‐area, and flexible displays but still suffer from the limited external quantum efficiency (EQE) below 5%. Herein, we demonstrate the EQE breakthrough by introducing a donor–acceptor type thermally activated delayed fluorescence (TADF) polymer as the sensitizer for the typical green‐emitting fluorescent dopants. Benefitting from their matched energy alignment, the unwanted trap‐assisted recombination directly on fluorescent dopant is prevented to avoid the additional loss of triplet excitons. Indeed, triplet excitons are mainly formed on the polymeric TADF sensitizer via a Langevin recombination and then spin‐flipped to singlet excitons due to the good upconversion capability. Followed by an efficient Förster energy transfer, both singlet and triplet excitons can be harvested by fluorescent dopants, leading to a promising solution‐processed green hyperfluorescence with a record‐high EQE of 21.2% (72.2 cd/A, 59.7 lm/W) and Commission Internationale de L'Eclairage coordinates of (0.32, 0.59). The results clearly highlight the great potential of solution‐processed fluorescent OLEDs based on TADF polymers as the sensitizer.

Conducting/semiconducting polymers feature an extended π-electron system in their main chains, enabling good conductivity and electroactivity. So they have great potential in solution processed blue lighting-emitting devices, such as polymer light-emitting diodes (PLEDs), quantum-dot light-emitting diodes (QLEDs) and perovskite light-emitting diodes (PeLEDs). This chapter summarizes the recent progress in polymeric materials, which are widely used as the emitting layer together with charge injection and transporting layers in these blue devices.

Organic solar cells (OSCs) processed without halogenated solvents and complex treatments are essential for future commercialization. Herein, we report three novel small molecule acceptors (NFAs) consisting of a Y6-like core but with 7C-extended naphthalene with progressively more chlorinated end-capping groups and a longer branched chain on the Nitrogen atom. These NFAs exhibit good solubilities in non -chlorinated organic solvents, broad optical absorptions, close 7C -7C stacking distances (3.63-3.84 angstrom), and high electron mobilities (-10-3 cm2 V-1 s-1). The o-xylene processed and as-cast binary devices using PM6 as the donor polymer exhibit a PCE increasing upon progressive chlorination of the naphthalene end-capping group from 8.93% for YN to 14.38% for YN-Cl to 15.00% for YN-2Cl. Furthermore similarly processed ternary OSCs were fabricated by employing YN-Cl and YN-2Cl as the third component of PM6:CH1007 blends (PCE = 15.75%). Compared to all binary devices, the ternary PM6:CH1007:YN-Cl (1:1:0.2) and PM6:CH1007:YN-2Cl (1:1:0.2) cells exhibit significantly improved PCEs of 16.49% and 15.88%, respectively, which are among the highest values reported to date for non-halogenated solvent processed OSCs without using any additives and blend post-deposition treatments.(c) 2022 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Pure organic phosphors capable of room-temperature phosphorescence show a great potential in organic light-emitting diodes, while it is limited by the big challenge to realize efficient electroluminescence under electric excitation. Herein, we develop a class of organic phosphors based on acridine as the electron donor, triazine as the electron acceptor and oxygen as the bridge between them. Benefitting from the characteristic donor-oxygen-acceptor geometry, these compounds are found to behave an exciting aggregation-induced organic room-temperature electrophosphorescence, and achieve a record-high external quantum efficiency of 15.8% for non-doped devices. Furthermore, they can sensitize multi-resonant emitters in the absence of any additional wide bandgap host, leading to an effective narrowband emission with a peak external quantum efficiency of 26.4% and a small full-width at half maximum of 26 nm. The results clearly indicate that donor-oxygen-acceptor geometry is a promising strategy to design organic phosphors suitable for organic light-emitting diodes.