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To achieve high efficiency and reliability in thermally activated delayed fluorescence (TADF) and phosphorescent organic light-emitting diodes (OLEDs), developing a novel host system has emerged as a critical research theme. In this study, we synthesized CzCzPh-mAd (9-(3-((1s,3s)-adamantan-1-yl)phenyl)-9H-3,9′-bicarbazole) as a p-type host by incorporating a bulky adamantane moiety fused with three cyclohexanes into CzCzPh (9-phenyl-9H-3,9′-bicarbazole). By incorporating a large and rigid adamantane group into the CzCzPh host (CzCzPh-mAd), we aimed to maintain the electrochemical and photophysical properties of CzCzPh while increasing its molecular weight, film-forming characteristics, and thermal stability. Ultimately, the solution-processed narrowband blue TADF-OLED employing the CzCzPh-mAd host exhibited a high external quantum efficiency greater than 13% and demonstrated superior thermal stability and reproducibility in device efficiency compared to devices based on CzCzPh. [ABSTRACT FROM AUTHOR]

In addition to the power conversion efficiency (PCE) of polymer solar cells (PSCs), long-term stability is a critical requirement. In this study, a crosslinkable PM6-based polymer donor, PM6-X30, was developed by introducing photocrosslinkable side chains into the PM6 polymer backbone. The new PM6-X30 retained the fundamental properties of the high-performance PM6 backbone. The crosslinking reaction was induced under the mild condition of UV 365 nm irradiation for 10 min, forming a stable polymer network to lock the internal morphology of the active layer. The PSC fabricated with the crosslinked PM6-X30:Y6-BO active layer exhibited a high PCE of 12.33%. Subsequently, this device sustained more than 80% of its original PCE after thermal aging at 80 °C for 180 min, while the non-crosslinked device and the reference device based on PM6-X0 could only retain 27.7 and 42.9% of their PCE, respectively, under the same aging conditions. This work demonstrates a promising strategy for boosting the long-term stability of high-performance PSCs, even at a slight sacrifice of the maximum PCE. [ABSTRACT FROM AUTHOR]

In this study, two polymeric host materials, P(NmCP) and P(mCP), were synthesized, and high-performing sky-blue and green thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs) were achieved. The simple structure polymer host was designed by inserting a pyridine group into the core of P(NmCP) and an electron-donating phenyl group into the core of P(mCP). The two polymeric hosts exhibited high triplet energies (T1 = 3.04 eV for P(NmCP) and 3.05 eV for P(mCP)), which were sufficiently high to realize blue and green TADF-OLEDs. In brief, solution-processed OLEDs with an emissive layer bearing P(NmCP) as a bipolar electron host exhibited remarkable performance with a maximum current efficiency (CE), power efficiency (PE), and external quantum efficiency (EQE) of 70.36 cd A−1, 63.15 lm W−1, and 20.07%, respectively, in the green-emitting device. In the blue-emitting device, we obtained a maximum CE, PE, and EQE of 27.13 cd A−1, 22.30 lm W−1, and 10.70%, respectively. The polymer design with such a high T1 value is believed to be the cornerstone for implementing high-performance TADF-OLEDs via solution processing in the future. [ABSTRACT FROM AUTHOR]

We successfully synthesized a crystalline main chain conjugated copolymer, P(BDBT-co-NDI2T), having BDBT donor-NDI2T acceptor heterojunctions in the film state. Interestingly, the polymer exhibited a strong absorption band from 500 to 650 nm, which overlapped well with the emission spectrum of white light-emitting diodes (LEDs) used as an indoor light source. The P(BDBT-co-NDI2T) films had a relatively smooth surface and internal morphology compared to the blend films of P(BDBT) and P(NDI2T). In particular, the Kelvin probe force microscopy data explained the increased uniformity in the distribution of the surface charge in the annealed P(BDBT-co-NDI2T) films as compared to those of the annealed blend films of P(BDBT) and P(NDI2T). Indoor photovoltaics (IPVs) produced by using the P(BDBT-co-NDI2T) synthesized in this study as an active layer showed a high power conversion efficiency of 12.70% (@500 lux) with a short circuit current density of 49.89 μA cm−2. The PCE of the P(BDBT-co-NDI2T) film-based IPVs was twice as high as that of the blend film-based IPVs and showed excellent operational stability. This study is the first time that the P(BDBT-co-NDI2T) has been applied in IPVs, which suggests the potential for their widespread use in the development of indoor organic PVs in the future. [ABSTRACT FROM AUTHOR]

The use of soluble host materials and thermally activated delayed fluorescence (TADF) emitters is indispensable for developing high-efficiency organic light-emitting diodes (OLEDs) by cost-effective solution processes. In this study, two bipolar hosts were designed as structural isomers, namely 3-(3,5-di(9H-carbazol-9-yl)phenyl)-9H-xanthen-9-one (Xp-mCP) and 2-(3,5-di(9H-carbazol-9-yl)phenyl)-9H-xanthen-9-one (Xm-mCP). The two host materials were synthesized by combining the unipolar host, 1,3-di(9H-carbazol-9-yl)benzene (mCP) with 9H-xanthen-9-one as an electron-accepting moiety. The two hosts exhibit good solubility in various organic solvents and high triplet energy (ET = 2.67 eV for Xp-mCP and ET = 2.82 eV for Xm-mCP), which renders them suitable for t4CzIPN-containing solution-processable green TADF-OLEDs. The maximum external quantum efficiency (EQE) values were 19.3% and 22.0% for Xp-mCP- and Xm-mCP-based green TADF-OLED, respectively. Among them, the device comprising Xm-mCP showed an excellent efficiency roll-off behavior by displaying only a 4.5% decrease and 11.4% decrease at 1000 cd m−2 and 2000 cd m−2, respectively. These results show the significant potential of xanthone-mCP host materials to develop solution-processable OLED technologies. [ABSTRACT FROM AUTHOR]

A new photocrosslinkable hole-transporting homopolymer (PX2Cz) was successfully synthesized using 9-((3-methyloxetan-3-yl)methyl)-9′-(4-vinylbenzyl)-9H,9′H-3,3′-bicarbazole monomer via radical polymerization. Biscarbazole, as a hole-transporting material, has two reactive sites that can introduce a radical polymerizable styrene moiety and a photocrosslinkable oxetane moiety. The photocuring temperature and time for the PX2Cz film was optimized to be 120 °C and 10 s. The photocured films showed good solvent resistance, which is favorable for the deposition of an emitting-layer solution on them. In particular, the highest occupied molecular orbital (HOMO) energy of the as-cast PX2Cz film was determined to be −5.37 eV which remained unchanged even after photocuring, thus facilitating hole transportation from the hole-injection layer. Subsequently, solution-processed, green, thermally activated delayed fluorescent organic light-emitting diodes (TADF-OLEDs) were manufactured using PX2Cz as the hole-transport material. The devices displayed a notable performance with an exceptionally low turn-on voltage (Von) of only 2.8 V and a high external quantum efficiency (EQE) of 22.5%; these values are substantially better than those of commonly used poly(9-vinylcarbazole) (PVK)-based OLEDs (Von = 3.6 V, EQE of 15.5%). The remarkably low turn-on voltage and high EQE were ascribed to the shallower HOMO energy level and more pronounced hole-transport ability of the photocured PX2Cz film. [ABSTRACT FROM AUTHOR]

The development of bipolar host materials for solution-processable thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs) is challenging because few host materials for TADF-OLEDs have been reported. Solution-processable bipolar host materials should have good solubility in various organic solvents and should exhibit good thermal stability and film-forming properties. In this study, three bipolar host materials (i.e.Py2Cz, Py2BFCz, and Py2ICz) for solution-processable green-emitting TADF-OLEDs were synthesized by coupling 2,4-diphenylpyrimidine to mCP and modifying the carbazole-donating units in the mCP structure. Thus, the effects of different host structures on the performance of green TADF-OLEDs could be investigated. The three host materials exhibited high thermal stability and fine morphologies in film states. Therefore, all three host materials were utilized to fabricate solution-processed green TADF-OLEDs with a green-emitting dopant. Particularly, the Py2ICz-based device displayed outstanding performance with a maximum external efficiency of 24.1% because Py2ICz has superior charge balance in the emitting layer than the others. These results unambiguously demonstrated that mCP derivatives with a pyrimidine core are suitable bipolar host materials for solution-processed green TADF-OLEDs. [ABSTRACT FROM AUTHOR]

Highly soluble functional materials acting as hosts for thermally activated delayed-fluorescence (TADF) emitters are urgently needed to stimulate the development of cost-effective, solution-processable, high-performance organic light-emitting diodes (OLEDs). An organic material, 10-(6-(9H-carbazol-9-yl)pyridin-3-yl)-9,9-diphenyl-9,10-dihydroacridine (APC), was designed and facilely synthesized by integrating electron-donating diphenyl acridine and carbazoles at the 2- and 5-positions of electron-accepting pyridine (D–A–D′ type architecture). The high triplet energy (2.82 eV), thermal robustness (thermal decomposition beyond 350 °C), appropriate highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels, balanced charge-carrier transport ability, and good solubility of APC supported its designation as a host material for solution-processable TADF-OLEDs. Two different types of TADF OLEDs were fabricated by varying the hole transport material (HTM) while consistently using APC as the host and familiar t4CzIPN as the green TADF emitter, and their device characteristics were compared. At first, the devices fabricated using PVK as HTM (ITO/PEDOT:PSS/PVK/EML/TPBi/LiF/Al) that could use an orthogonal solvent system displayed a state-of-the-art performance with external quantum efficiency (EQE)/current efficiency (CE)/power efficiency (PE) as high as 24.0%/82.2 cd A−1/46.9 lm W−1, respectively. In particular, over 90.0% of EQE was retained (EQE of 21.7%) at the practical luminance of 1000 cd m−2, which is advantageous for display technology. Another class of devices was fabricated by replacing PVK with our recently reported thermally cross-linkable X-TPACz as the HTM, realizing a very low turn-on voltage (2.9 V) and excellent PE of 70.1 lm W−1 (with a similar EQE of 22.8%), which could be very effective for lighting equipment. These excellent outcomes demonstrate the potential of APC as a host material for future solution-processable display and lighting technologies. [ABSTRACT FROM AUTHOR]

This study reports the design, synthesis, and characterization of two new bipolar host materials, DCzCP and TCzCP. Both materials were implemented as hosts by doping a known green thermally activated delayed fluorescent (TADF) emitter (t4CzIPN) in solution-processable OLEDs. DCzCP-based devices afford the best performance with the maximum external quantum efficiency (EQE) of 21.2%. Notably, the EQE was maintained at 20.7% and 19.7% at a practical luminance of 500 cd m−2 and 1000 cd m−2, respectively, demonstrating very small roll-off. [ABSTRACT FROM AUTHOR]

Conjugated block copolymers containing donor (D) and acceptor (A) blocks have high potential for single component polymer solar cells (SC-PSCs), but still exhibit the complexity of polymer synthesis and low device efficiency. In this research, we successfully synthesized a new fully conjugated D–A block copolymer (CDABP) by performing the entire reaction in one-pot from start to completion. This polymerization method has the advantage of saving synthesis time and cost. The photoluminescence (PL) of the CDABP film was completely quenched due to photoinduced inter/intramolecular charge transfer. A single component polymer solar cell (SC-PSC) with a CDABP film annealed at 180 °C showed the maximum power conversion efficiency (PCE) of 5.28%, a high short circuit current of 10.77 mA cm−2 and a fill factor of 62.86%, which is much higher than that (2.62%) of the device with the as-cast film. This performance can be attributed to its fine internal/surface morphology and high crystallinity of the CDABP film. In addition, transient absorption experiments on the CDABP films showed that charge carrier generation is faster and the lifetime of the generated charge carriers is longer in the annealed film than in the as-cast film. Our research explicitly provides a new structural design and simple synthesis strategy for D–A conjugate block copolymers for high-efficiency SC-PSCs. [ABSTRACT FROM AUTHOR]

A light-emitting molecular triad (BPCP-2CPC) with dual functionality was successfully synthesized and applied to solution-processed non-doped organic light-emitting diodes. The BPCP-2CPC triad contains 9-phenyl-9H-carbazole units as a host moiety tethered to a green-emitting core (BPCP) through a cyclohexane unit and exhibits thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) characteristics simultaneously. The BPCP-2CPC-based non-doped TADF-OLED devices showed a high external quantum efficiency (EQE) of 13.4%. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) materials have attracted significant attention owing to their state-of-the-art performance in the field of organic light-emitting diodes (OLEDs). TADF materials have the capability of harvesting both singlet and triplet excitons through reverse intersystem crossing, thus, the maximum internal quantum efficiency can be expected to be 100%. Thanks to TADF materials that are developed from pure organic entities so that they are inexpensive and external quantum efficiencies as high as 38% have been achieved to date. Despite the high performance of doped OLEDs, precise control of the host–guest ratio and phase separation at high driving voltages are the foremost challenges. In order to circumvent these demerits, the use of numerous small molecules, dendritic molecules, and polymers as non-doped emitters has been reported. Non-doped OLEDs consist of only a single molecule emitter in the emissive layer, thus simplifying the device fabrication process. Furthermore, non-doped OLEDs exhibit better device stability compared to doped devices, because the former do not exhibit phase separation or crystallinity and maintain a homogeneous surface film morphology during device operation. As a result, non-doped OLEDs are capable of overcoming the most pivotal issues of device complexity and stability, which makes them effective in rendering OLEDs commercially viable. Although maximum external quantum efficiencies of nearly 23.0% in blue, 22.0% in green, 22.0% in yellow, 17.0% in orange, and 10.0% in red emitting materials have been realized with non-doped OLEDs, still further progress is essential to reach the doped devices. This review systematically describes the molecular design, photophysical properties, and electroluminescence performance data of non-doped TADF emitters. We strongly believe that this review will be beneficial in terms of presenting a specific direction for the design of a variety of non-doped TADF emitters in the near future. [ABSTRACT FROM AUTHOR]

A series of conjugated terpolymers, P2–P4, based on 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene as the electron-donating unit, methyl-3-thiophenecarboxylate (3MT) as the weak electron-accepting unit, and 1,3-bis(2-ethylhexyl)benzo[1,2-c:4,5-c′]dithiophene-4,8-dione (BDD) as the strong electron-accepting unit were synthesized to investigate the effect of the contents of 3MT and BDD on their optical and electrochemical properties and the performance of the derived fullerene-free polymer solar cell (PSC) devices. By varying the contents of 3MT and BDD in the terpolymer structure, the solubility, absorption range, and energy levels could be efficiently tuned. Among the three terpolymers, the as-cast blend film of P3:acceptor with complementary absorption and favorable internal morphology exhibited the highest power conversion efficiency of 10.26% with a high open circuit voltage of 0.94 V and short circuit current density of 17.18 mA cm−2 in the PSC. Although the three repeating units were randomly arranged along the polymer backbone, their PSCs exhibited an excellent shelf-life of over 1000 h under ambient conditions, which is as good as those of binary D–A copolymers. [ABSTRACT FROM AUTHOR]

New versatile host materials with good solubility in common organic solvents are greatly desired to promote solution-processable thermally activated delayed fluorescence organic light-emitting diodes. This paper describes the design and synthesis of two new host materials, namely 3′-(9H-carbazol-9-yl)-[1,1′-biphenyl]-3,5-diylbis(diphenylphosphine oxide) (CDPO) and 3′,5′-di-(9H-carbazol-9-yl)-[1,1′-biphenyl]-3,5-diylbis (diphenylphosphine oxide) (mCPDPO), featuring hole-transporting carbazole and electron-transporting diphenylphosphine oxide (DPO) entities. The donor strength was varied to a constant n-type DPO core to tune the functional properties. The detailed studies proved that the resulting two new materials exhibit excellent solubility in common organic solvents, high triplet energy (＞2.80 eV), high glass transition temperature (up to 133 °C), and good bipolar electronic nature. Consequently, both compounds were used as hosts in solution-processable blue and green thermally activated delayed fluorescence (TADF) OLEDs. In particular, the devices using mCPDPO as a host in the emissive layer showed outstanding performance with a maximum current efficiency, power efficiency, and external quantum efficiency of 35.3 cd A−1, 17.0 lm W−1 and 15.4% in the blue-emitting diode, and 61.5 cd A−1, 29.7 lm W−1 and 18.8% in the green-emitting diode, respectively. These results corroborated the potential of carbazole-phosphine oxide derivatives as host materials in solution-processable blue and green TADF OLEDs. [ABSTRACT FROM AUTHOR]

A new A-b-D-b-A-type n-type small molecule, IDT-3MT, was synthesized bearing a weak acceptor thiophene-3-carboxylate bridge (3MT = b) between indacenodithiophene as a donating core and 2-(3-oxo-2,3-dihydroinden-1-ylidene)-malononitrile as the accepting end groups. Compared to IDT-T bearing a neat thiophene bridge, IDT-3MT displayed a red-shifted absorption spectrum in the film state, which is a more effective complementary absorption behavior with PBDB-T as the donor material. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels of IDT-3MT became correspondingly lower. Based on the results of grazing-incidence wide-angle X-ray scattering, the blend film of PBDB-T:IDT-3MT exhibited a more prominent face-on orientation and fine surface morphology compared with PBDB-T:IDT-T, which can facilitate charge transportation in the vertical direction. Among the two acceptors, the polymer solar cell based on a solvent additive-free as-cast PBDB-T:IDT-3MT blend film exhibited the highest power conversion efficiency of 8.40% with a high open-circuit voltage of 0.95 V and a short-circuit current density of 14.43 mA cm−2 due to the more prominent face-on orientation and favorable morphology of the blend film. According to the simple structural modification of the acceptor molecule, the ester group in the thiophene bridge played an important role toward achieving high-performance polymer solar cells. [ABSTRACT FROM AUTHOR]

A novel conjugated terpolymer referred to as Ter-3MTTPD was successfully synthesized using 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene as a donor and methyl thiophene-3-carboxylate (3MT) and 5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (TPD) as acceptor units to investigate the effects of the terpolymer structure on the optical and electrochemical properties. The performance of an all-polymer solar cell (all-PSC) was comprehensively examined by blending the terpolymer with 2,7-bis(2-hexyldecyl)-4-(selenophen-2-yl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (NDI-Se). The as-cast blend film of Ter-3MTTPD:NDI-Se exhibits the highest power conversion efficiency of 7.66% in the all-PSC. This was further supported by the results of time-resolved photoluminescence (TRPL) in Ter-3MTTPD:NDI-Se blend film states which yielded the highest PL quenching efficiency (90%) resulting from the shortest average lifetime, τave of ∼67 ps, much smaller than those of the two binary copolymer blend films (e.g., τave = 194 ps and 149 ps, respectively, for Co-3MT:NDI-Se and Co-TPD:NDI-Se). In addition, for an as-cast blend film of Ter-3MTTPD:NDI-Se in the active layer, the shelf-life (∼1000 h) of the all-PSC under ambient conditions was found to be much better compared to those of PSCs based on the other two binary copolymers, Co-3MT and Co-TPD. [ABSTRACT FROM AUTHOR]

Solution-processable thermally activated delayed fluorescence (TADF)-assisted materials have been identified as promising materials for future applications as organic light-emitting diodes (OLEDs) owing to their numerous advantageous such as easy fabrication, large area applications, low cost, and state-of-the-art performance. Herein, two new carbazole-dendronized TADF emitters, namely, TB2CZ-ACTRZ and TB14CZ-ACTRZ, were designed and synthesized. Two different-sized carbazole dendron wedges were utilized as the encapsulating groups for the TADF core via methylene groups. The influence of the encapsulated dendrons on the thermal, optical, electrochemical, and OLED device performances of both dendritic molecules was studied in detail. The photophysical studies of TB2CZ-ACTRZ and TB14CZ-ACTRZ disclosed their extremely small singlet–triplet energy gaps (ΔEST) of 79 and 134 meV, respectively. Consequently, the solution-processed non-doped OLEDs without any hole injection/transport layers featuring TB2CZ-ACTRZ and TB14CZ-ACTRZ as the TADF emitters demonstrated the maximum external quantum efficiencies (EQEs) of 9.5 and 8.1%, respectively, while the device fabricated with their simple emissive core ACTRZ had an EQE of only 1.2%. These results clearly demonstrated that the development of multifunctional TADF dendritic emitters is an extremely worthwhile objective for the realization of highly efficient solution-processable non-doped OLEDs with simple device architectures. [ABSTRACT FROM AUTHOR]

Three new derivatives containing silane cores, viz. 9,9′,9′′-(((4-(pyridin-3-yl)phenyl)silanetriyl)tris(benzene-4,1-diyl))tris(9H-carbazole) (SiCz3Py1), bis(4-(9H-carbazol-9-yl)phenyl)bis(4-(pyridin-3-yl)phenyl)silane (SiCz2Py2), and 9-(4-(tris(4-(pyridin-3-yl)phenyl)silyl)phenyl)-9H-carbazole (SiCz1Py3), were designed and synthesized. Carbazole as a donor and pyridine as an acceptor were tethered to tetraphenylsilane at different mole ratios. All three host materials showed high glass transition temperatures between 118 and 164 °C, which are different from those of the previous silane-based host materials (e.g., diphenyldi-o-tolylsilane (UGH-1), 1,4-bis(triphenylsilyl)benzene (UGH-2), and 1,3-bis(triphenylsilyl)benzene (UGH-3)). The triplet energies of these three hosts are observed at 2.85–2.90 eV, which is high enough for them to act as blue host materials in thermally activated delayed fluorescence organic light emitting diodes (TADF OLEDs). In particular, SiCz2Py2 and SiCz1Py3 hosted-TADF OLEDs demonstrated excellent performances, with a maximum external quantum efficiency (EQEmax) of 18.7 and 18.8%, respectively. Such good performances of SiCz2Py2 and SiCz1Py3 are originated by suppressing the non-radiative triplet decay and high reverse intersystem crossing (RISC) rate constant for efficient triplet to singlet up-conversion. This work demonstrates that tetraphenylsilane is a promising non-conjugate (i.e., sp3-hybridized) linkage core for developing a variety of high Tg host materials, particularly for blue TADF OLEDs. [ABSTRACT FROM AUTHOR]

We synthesized two types of novel poly(3-alkylthiophene)-free (D)n-b-(A)m conjugated block copolymers: PTQI-block-PNDISs. PTQI-b-PNDIS is the fully conjugated block copolymer, in which the donor block is connected to the acceptor block via a π-conjugated unit. In addition, the donor block was connected to an acceptor block through a non-conjugated alkylene spacer, yielding PTQI-b-PNDISL, which is a partially conjugated block copolymer. The power conversion efficiency (PCE) was 1.54% with an open-circuit voltage of 0.79 V in the single-component polymer solar cell (PSC) based on PTQI-b-PNDISL, better performance than that of the PSC containing PTQI-b-PNDIS (PCE ∼ 0.36%). These results reveal the potential for improving the photovoltaic performance in PSCs by controlling the internal morphology with exploitation of the self-segregating behavior of p- and n-blocks in the film state. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of the geometries of perylene diimide (PDI)-based small molecules, five different isomers were synthesized by using a cyclohexane core as a simple sp3-σ core. Diaminocylohexane is such an effective core for the systematic development of many kinds of isomers via geometric tuning as well as for reducing the self-aggregation tendency of PDIs. Depending on the anchoring position of the PDI units on the cyclohexane core (ortho-, meta- and para-), isomers exhibited differences in solubility and crystallinity. Among the studied isomers, ortho-substituted t-OCP was found to have a highly twisted molecular structure which minimizes the strong tendency towards crystallization due to individual PDI moieties. The unique geometrical nature of the t-OCP isomer led to the highest power conversion efficiency (PCE = 6.23%) of bulk heterojunction (BHJ) polymer solar cells (PSCs) with a higher short-circuit current density (Jsc) and fill factor (FF). It is mainly ascribed to the formation of a nanophase interpenetrating network with well-balanced carrier mobility in the blend film. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) materials have attracted much attention in the field of organic light-emitting diodes (OLEDs), with their state-of-the-art performance in terms of external quantum efficiencies (EQEs), turn-on voltages, and color coordinates. TADF materials exhibited EQEs above 25% due to harvesting both singlet and triplet excitons via reverse intersystem crossing (RISC). A small singlet–triplet energy gap (ΔEST) is essential for TADF materials to exhibit efficient upconversion from the lowest triplet excited state (T1) to the lowest singlet excited state (S1, T1→ S1). Moreover, these materials are purely organic and thus not costly. Therefore, the TADF approach provides the best alternative to conventional fluorescent and phosphorescent OLEDs, regarding device efficiency and cost. On the other hand, blue light-emitting devices are facing several issues related to their stability and efficiency, making their development quite challenging for researchers. Herein, we review the recent advances in the use of blue TADF dopants and hosts in OLEDs. [ABSTRACT FROM AUTHOR]

We propose a novel tricyanovinyldihydrofuran (TCF)-based molecule called DBOB-DTCF that is designed and synthesized for application in n-type field-effect transistors (FETs). It can be operated in a stable manner under ambient conditions. DBOB-DTCF is successfully fabricated as crystalline microplates (CMs) because of its capability of self-assembly. A high electron mobility of ∼1.9 cm2 V−1 s−1 is observed for a CM-based FET, measured under ambient conditions. This suggests that TCF is an excellent acceptor unit that organizes air stable n-type organic semiconductors. [ABSTRACT FROM AUTHOR]

New M- and V-shaped perylene diimide (PDI)-based small molecules using a non-conjugated 1,1-diphenylcyclohexane linker (CP-M and CP-V, respectively) were designed and synthesized as new n-type acceptors for nonfullerene-based polymer solar cells. The blended film with poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole)] (PPDT2FBT) and CP-V displayed a higher power conversion efficiency of 5.28% due to higher short circuit current and fill factor values. [ABSTRACT FROM AUTHOR]

New bipolar host molecules composed of carbazole, pyridoindole, and dibenzothiophene (DBT) were synthesized for blue thermally activated delayed fluorescence (TADF)-based organic light-emitting diodes (OLEDs). 2,8-Di(9H-carbazol-9-yl)dibenzo[b,d]thiophene, 9-(8-(9H-carbazol-9-yl)dibenzo[b,d]thiophen-2-yl)-9H-pyrido[2,3-b]indole, and 2,8-bis(9H-pyrido[2,3-b]indol-9-yl)dibenzo[b,d]thiophene were prepared based on the selective reactivity at the 2,8-positions of DBT. The new symmetric and asymmetric host materials exhibited high triplet energies (2.89–2.95 eV). 4,5-Di(9H-carbazol-9-yl)phthalonitrile (2CzPN) was selected as an emitting dopant for achieving sky-blue emissions in TADF-OLEDs. 2CzPN-doped TADF-OLEDs, whose configuration is ITO (50 nm)/HATCN (7 nm)/TAPC (75 nm)/host:6% 2CzPN (20 nm)/TmPyPB (50 nm)/LiF (15 nm)/Al (100 nm), showed low driving voltages and high external quantum efficiencies (EQEs). These results are attributed to the well-controlled bipolar character of the host giving a better charge balance in the emitting layer. In particular, the device containing ZDN:6% 2CzPN showed an unprecedentedly high EQE of 25.7% (at 0.074 mA cm−2). [ABSTRACT FROM AUTHOR]

A new diketopyrrolopyrrole (DPP)-based π-conjugated copolymer containing terselenophene units has been successfully synthesized. Its hole mobility reaches around 5.0 cm2 V−1 s−1 in thin film transistors made from thermally annealed films. This proves that a longer terselenophene unit induced excellent charge transport properties. [ABSTRACT FROM AUTHOR]

A novel bipolar host 9-(4-(9H-pyrido[2,3-b]indol-9-yl)phenyl)-9H-3,9′-bicarbazole (pBCb2Cz) was prepared for high efficiency blue phosphorescent organic light-emitting diodes (PhOLEDs), a high triplet energy (ET) material, employing electron-deficient α-carboline. pBCb2Cz (ET = 2.93 eV) was effective as a host material for FIrpic- and FCNIrpic-based blue PhOLEDs, and highest quantum efficiencies of 23.0 and 16.2%, respectively, were achieved. [ABSTRACT FROM AUTHOR]

Novel donor–acceptor π-conjugated copolymers, P(DPP-BDT) and P(DPP-ANT), were synthesized in 87–89% yield. Thin-film transistors (TFTs) made from the thermally annealed film of P(DPP-ANT) exhibited much better performance (e.g., μmax = 1.90 cm2 V−1 s−1, Ion/off≈ 106) than those made from the thermally annealed film of P(DPP-BDT). [ABSTRACT FROM AUTHOR]

New anthracene-based X-shaped conjugated molecules 1and 2for use as highly soluble p-type organic semiconductors were developed and exhibited large field-effect mobilities of 0.04 cm2V−1s−1(Ion/Ioff= 2.8 × 105) and 0.24 cm2V−1s−1(Ion/Ioff= 5.4 × 106) for devices of 1and 2, respectively. [ABSTRACT FROM AUTHOR]

Correction for ‘Novel dendritic large molecules as solution-processable thermally activated delayed fluorescent emitters for simple structured non-doped organic light emitting diodes’ by Mallesham Godumala et al., J. Mater. Chem. C, 2018, 6, 1160–1170. [ABSTRACT FROM AUTHOR]

Correction for ‘Thermally activated delayed fluorescence blue dopants and hosts: from the design strategy to organic light-emitting diode applications’ by Mallesham Godumala et al., J. Mater. Chem. C, 2016, DOI: URL10.1039/c6tc04377a/URL. [ABSTRACT FROM AUTHOR]

A bifunctional fluorescent probe based on a carbazole-pyrimidine conjugate for Hg(2+) and Cu(2+) detection was designed and synthesized. Probe 3 exhibits red shifts in its absorption and fluorescence spectra with significant visual color changes in the presence of these ions. The detection limits of probe 3 for these metal ions were in the nanomolar range. The probe could also be useful as a solid optical sensor for Hg(2+) and Cu(2+).

A new bitellurophene-based π-conjugated polymer (PDPPBTe) was synthesized and its semiconducting property was utilized for detecting Br2. The PDPPBTe polymer exhibited a highly sensitive response to Br2, which was indicated by a significant variation of the drain current in thin-film transistors.

A new tellurophene-based π-conjugated polymer, PDTDPPTe, was synthesized. PDTDPPTe exhibits a smaller optical band gap (E(g)(opt) = 1.25 eV) than thiophene-based PDTDPPT (E(g)(opt) = 1.30 eV). Thin-film transistors comprising PDTDPPTe displayed outstanding performance (μ(max) = 1.78 cm(2) V(-1) s(-1), I(on)/I(off) = 10(5-6)).

A new pyrene-cored π-conjugated molecule has been synthesized through Sonogashira coupling reaction. The single-crystalline microribbon-based FET exhibited the highest mobility of 0.7 cm(2) V(-1) s(-1) (I(on)/I(off) > 10(6)). Single-crystalline microribbons were employed to operate in an organic phototransistor (OPT) under very low light intensity (I = 5.6 μW cm(-2))., (This journal is © The Royal Society of Chemistry 2011)