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.
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.
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.
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.
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.
Photomultiplication‐type organic photodetectors (PM‐OPDs) with high external quantum efficiency (EQE) of over 100% are attracting increasing attention due to their potential importance in detecting ...weak incident light. Considering that the gain of PM‐OPD is determined by the ratio of carrier lifetime over carrier transit time, a systematic study on the effect of the end‐functionalization of a new extended aromatic fused‐ring non‐fullerene acceptor (NFA) on the carrier trap/transit time of the PM‐OPD. Photophysical analyses by means of ultraviolet‐visible absorption, ultraviolet photoelectron spectroscopy, and photoluminescence combined with structural analyses through grazing‐incidence wide‐angle X‐ray scattering show that fluorination of the NFA with the deepest lowest unoccupied molecular orbital level and non‐isotropic molecular ordering can yield the longest carrier lifetime. Furthermore, surface energy study show that fluorination of the NFA can also yield the most hydrophobic nature, which can allow the most efficient injection barrier thinning/lowering of the active layer/cathode interface under illumination due to the localized acceptor distribution toward cathode, maximizing the hole injection efficiency from cathode. As a result, an unprecedentedly high EQE of 156 000% is obtained from the optimized PM‐OPD. This work shows the importance of the molecular design of acceptor molecules in fabricating high‐performance PM‐OPDs.
A series of new non‐fullerene acceptors (NFAs) with a large fused aromatic system are synthesized and used as electron‐trapping acceptors for realizing high‐performance photomultiplication‐type organic photodetectors (PM‐OPDs). The end‐functionalization of the extended fused‐ring NFA significantly affect the charge carrier lifetime of the resulting PM‐OPDs and preferentially focused acceptor distribution. Consequently, an unprecedentedly high external quantum efficiency over 150 000% is achieved.
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