New blue (DBA‐SAB) and deep‐blue (TDBA‐SAF) thermally activated delayed fluorescence (TADF) emitters are synthesized for blue‐emitting organic‐light emitting diodes (OLEDs) by incorporating ...spiro‐biacridine and spiro‐acridine fluorene donor units with an oxygen‐bridged boron acceptor unit, respectively. The molecules show blue and deep‐blue emission because of the deep highest occupied molecular energy levels of the donor units. Besides, both emitters exhibit narrow emission spectra with the full‐width at half maximum (FWHM) of less than 65 nm due to the rigid donor and acceptor units. In addition, the long molecular structure along the transition dipole moment direction results in a high horizontal emitting dipole ratio over 80%. By combining the effects, the OLED utilizing DBA‐SAB as the emitter exhibits a maximum external quantum efficiency (EQE) of 25.7% and 1931 Commission Internationale de l'éclairage (CIE) coordinates of (0.144, 0.212). Even a higher efficiency deep blue TADF OLED with a maximum EQE of 28.2% and CIE coordinates of (0.142, 0.090) is realized using TDBA‐SAF as the emitter.
New blue‐emitting thermally activated delayed fluorescence (TADF) emitters are designed and synthesized for blue‐emitting organic light‐emitting diodes (OLEDs) by incorporating rigid donor units with an oxygen‐bridged boron acceptor unit. As a result, a deep‐blue OLED with a maximum external quantum efficiency of 29.3% and CIE coordinates of (0.142, 0.090) is realized.
All‐polymer solar cells (all‐PSCs) are a highly attractive class of photovoltaics for wearable and portable electronics due to their excellent morphological and mechanical stabilities. Recently, new ...types of polymer acceptors (PAs) consisting of non‐fullerene small molecule acceptors (NFSMAs) with strong light absorption have been proposed to enhance the power conversion efficiency (PCE) of all‐PSCs. However, polymerization of NFSMAs often reduces entropy of mixing in PSC blends and prevents the formation of intermixed blend domains required for efficient charge generation and morphological stability. One approach to increase compatibility in these systems is to design PAs that contain the same building blocks as their polymer donor (PD) counterparts. Here, a series of NFSMA‐based PAs P(BDT2BOY5‐X), (X = H, F, Cl) are reported, by copolymerizing NFSMA (Y5‐2BO) with benzodithiophene (BDT), a common donating unit in high‐performance PDs such as PBDB‐T. All‐PSC blends composed of PBDB‐T PD and P(BDT2BOY5‐X) PA show enhanced molecular compatibility, resulting in excellent morphological and electronic properties. Specifically, PBDB‐T:P(BDT2BOY5‐Cl) all‐PSC has a PCE of 11.12%, which is significantly higher than previous PBDB‐T:Y5‐2BO (7.02%) and PBDB‐T:P(NDI2OD‐T2) (6.00%) PSCs. Additionally, the increased compatibility of these all‐PSCs greatly improves their thermal stability and mechanical robustness. For example, the crack onset strain (COS) and toughness of the PBDB‐T:P(BDT2BOY5‐Cl) blend are 15.9% and 3.24 MJ m–3, respectively, in comparison to the PBDB‐T:Y5‐2BO blends at 2.21% and 0.32 MJ m–3.
A new class of polymer acceptors (PAs, P(BDT2BOY5‐X)) consisting of benzodithiophene (BDT) and non‐fullerene small molecule‐accepting units is developed, which shows excellent material compatibility with an efficient BDT‐based polymer donor (PD). The resulting all‐polymer solar cells show excellent photovoltaic efficiency, thermal stability, and mechanical robustness at the same time, benefitting from the high chemical and molecular compatibilities between PD and PA.
Deep‐blue emitting Iridium (Ir) complexes with horizontally oriented emitting dipoles are newly designed and synthesized through engineering of the ancillary ligand, where ...2′,6′‐difluoro‐4‐(trimethylsilyl)‐2,3′‐bipyridine (dfpysipy) is used as the main ligand. Introduction of a trimethylsilyl group at the pyridine and a nitrogen at the difluoropyrido group increases the bandgap of the emitter, resulting in deep‐blue emission. Addition of a methyl group (mpic) to a picolinate (pic) ancillary ligand or replacement of an acetate structure of pic with a perfluoromethyl‐triazole structure (fptz) increases the horizontal component of the emitting dipoles in sequence of mpic (86%) > fptz (77%) > pic (74%). The organic light‐emitting diode (OLED) using the Ir complex with the mpic ancillary ligand shows the highest external quantum efficiency (31.9%) among the reported blue OLEDs with a y‐coordinate value lower than 0.2 in the 1931 Commission Internationale de L'Eclairage (CIE) chromaticity diagram.
A deep‐blue iridium (Ir) complex with CIE coordinate y < 0.2 and horizontal emitting dipole ratio of 86% is developed by the chemical design of ancillary ligands. The phosphorescent organic light‐emitting diode (phOLED) using the Ir complex shows an external quantum efficiency of 31.9% with CIE y < 0.2, which is the highest value ever achieved in deep‐blue phOLEDs.
Triplet harvesting is important for the realization of high‐efficiency fluorescent organic light‐emitting diodes (OLEDs). Triplet–triplet annihilation (TTA) is one triplet‐harvesting strategy. ...However, for blue‐emitting anthracene derivatives, the theoretical maximum radiative singlet‐exciton ratio generated from the TTA process is known to be 15% in addition to the initially generated singlets of 25%, which is insufficient for high‐efficiency fluorescent devices. In this study, nearly 25% of the radiative singlet‐exciton ratio is realized by TTA using an anthracene derivative, breaking the theoretical limit. As a result, efficient deep‐blue TTA fluorescent devices are developed, exhibiting external quantum efficiencies of 10.2% and 8.6% with Commission Internationale de l'Eclairage color coordinates of (0.134, 0.131) and (0.137, 0.076), respectively. The theoretical model provided herein explains the experimental results considering both the TTA and reverse intersystem crossing to a singlet state from higher triplet states formed by the TTA, clearly demonstrating that the radiative singlet ratio generated from TTA can reach 37.5% (total radiative singlet‐exciton ratio: 62.5%), well above 15% (total 40%), despite the molecule having S1, T2 < 2T1 < Q1 energy levels, which will lead to the development of high‐efficiency fluorescent OLEDs with external quantum efficiencies exceeding 28% if the outcoupling efficiency is 45%.
The triplet–triplet annihilation (TTA) process can recycle nonradiative triplet excitons to radiative singlet excitons and enhance the efficiency of fluorescent organic light‐emitting diodes (OLEDs). Conventionally, the theoretical limit of delayed emission ratio by the TTA process is known to be 37.5% in anthracene‐based molecules. In this work, 48% of delayed emission ratio is achieved by TTA with carefully designed blue OLEDs.
A record‐breaking high electron mobility of 7.0 cm2V−1s−1 for n‐channel polymer OFETs is reported. By the incorporation of only one nitrile group as an electron‐withdrawing function in the vinyl ...linkage of the DPP‐based copolymer, a dramatic inversion of majority charge‐carriers from holes to electrons is achieved.
Charge carrier mobility is still the most challenging issue that should be overcome to realize everyday organic electronics in the near future. In this Communication, we show that introducing smart ...side-chain engineering to polymer semiconductors can facilitate intermolecular electronic communication. Two new polymers, P-29-DPPDBTE and P-29-DPPDTSE, which consist of a highly conductive diketopyrrolopyrrole backbone and an extended branching-position-adjusted side chain, showed unprecedented record high hole mobility of 12 cm2/(V·s). From photophysical and structural studies, we found that moving the branching position of the side chain away from the backbone of these polymers resulted in increased intermolecular interactions with extremely short π–π stacking distances, without compromising solubility of the polymers. As a result, high hole mobility could be achieved even in devices fabricated using the polymers at room temperature.
A new naphthalene diimide (NDI)‐based polymer with strong electron withdrawing dicyanothiophene (P(NDI2DT‐TTCN)) is developed as the electron transport layer (ETL) in place of the fullerene‐based ETL ...in inverted perovskite solar cells (Pero‐SCs). A combination of characterization techniques, including atomic force microscopy, scanning electron microscopy, grazing‐incidence wide‐angle X‐ray scattering, near‐edge X‐ray absorption fine‐structure spectroscopy, space‐charge‐limited current, electrochemical impedance spectroscopy, photoluminescence (PL), and time‐resolved PL decay, is used to demonstrate the interface phenomena between perovskite and P(NDI2DT‐TTCN) or 6,6‐phenyl‐C61‐butyric acid methyl ester (PCBM). It is found that P(NDI2DT‐TTCN) not only improves the electron extraction ability but also prevents ambient condition interference by forming a hydrophobic ETL surface. In addition, P(NDI2DT‐TTCN) has excellent mechanical stability compared to PCBM in flexible Pero‐SCs. With these improved functionalities, the performance of devices based on P(NDI2DT‐TTCN) significantly outperform those based on PCBM from 14.3 to 17.0%, which is the highest photovoltaic performance with negligible hysteresis in the field of polymeric ETLs.
A novel naphthalene diimide (NDI)‐based polymer (P(NDI2DT‐TTCN)) is used as the electron transport layer in inverted flexible perovskite solar cells. Photovoltaic performances of the P(NDI2DT‐TTCN)‐based device show a significant improvement up to 17.0%, whereas the control device for 6,6‐phenyl‐C61‐butyric acid methyl ester based device only shows power conversion efficiency of 14.3%. In addition, P(NDI2DT‐TTCN) improves not only the light‐induced and long‐term stability but also mechanical stability.
The use of natural or bioinspired materials to develop edible electronic devices is a potentially disruptive technology that can boost point‐of‐care testing. The technology exploits devices that can ...be safely ingested, along with pills or even food, and operated from within the gastrointestinal tract. Ingestible electronics can potentially target a significant number of biomedical applications, both as therapeutic and diagnostic tool, and this technology may also impact the food industry, by providing ingestible or food‐compatible electronic tags that can “smart” track goods and monitor their quality along the distribution chain. Temporary tattoo‐paper is hereby proposed as a simple and versatile platform for the integration of electronics onto food and pharmaceutical capsules. In particular, the fabrication of all‐printed organic field‐effect transistors on untreated commercial tattoo‐paper, and their subsequent transfer and operation on edible substrates with a complex nonplanar geometry is demonstrated.
Temporary tattoo‐paper is proposed as a simple and versatile platform for the integration of biocompatible organic electronics onto food and pharmaceutical capsules. The fabrication of all‐printed biocompatible organic transistors and complementary logic on untreated commercial tattoo‐paper, and their subsequent transfer to and operation on edible substrates is demonstrated, paving the way for novel point‐of‐care devices and smart food labels.
Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) molecules based on boron and nitrogen atoms are emerging as next‐generation blue emitters for organic light‐emitting diodes (OLEDs) ...due to their narrow emission spectra and triplet harvesting properties. However, intermolecular aggregation stemming from the planar structure of typical MR‐TADF molecules that leads to concentration quenching and broadened spectra limits the utilization of the full potential of MR‐TADF emitters. Herein, a deep‐blue MR‐TADF emitter, pBP‐DABNA‐Me, is developed to suppress intermolecular interactions effectively. Furthermore, photophysical investigation and theoretical calculations reveal that adding biphenyl moieties to the core body creates dense local triplet states in the vicinity of S1 and T1 energetically, letting the emitter harvest excitons efficiently. OLEDs based on pBP‐DABNA‐Me show a high external quantum efficiency (EQE) of 23.4% and a pure‐blue emission with a Commission Internationale de L'Eclairage (CIE) coordinate of (0.132, 0.092), which are maintained even at a high doping concentration of 100 wt%. Furthermore, by incorporating a conventional TADF sensitizer, deep‐blue OLEDs with a CIE value of (0.133, 0.109) and an extremely high EQE of 30.1% are realized. These findings provide insight into design strategies for developing efficient deep‐blue MR‐TADF emitters with fast triplet upconversion and suppressed self‐aggregation.
A multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitter exhibiting deep‐blue emission with Commission Internationale de L'Eclairage coordinates of (0.132, 0.092), narrow full width at half maximum of 22 nm, and high external quantum efficiency of 23.4% is developed by introducing bulky biphenyls and N‐biphenyl‐N‐ortho‐dimethylphenylamine that create dense local triplet states and suppress intramolecular aggregation.
A new polymeric semiconductor, PDPPDTSE, is reported which is composed of a diketopyrrolopyrrole moiety and selenophenylene vinylene selenophene, with a high field‐effect mobility achieved through ...intermolecular donor–acceptor interactions. The field‐effect mobility of OFET devices based on PDPPDTSE by spin‐casting is 4.97 cm2 V−1 s−1, which is higher than predecessor polymeric semiconductors.
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