A deep-red fluorophore based on naphthothiadiazole as emitter with hybridized local and charge transfer and ambipolar transporting properties for electroluminescent devices

• Suangsiri Arunlimsawat,
• Patteera Funchien,
• Pongsakorn Chasing,
• Atthapon Saenubol,
• Taweesak Sudyoadsuk and
• Vinich Promarak

Beilstein J. Org. Chem. 2023, 19, 1664–1676, doi:10.3762/bjoc.19.122

• demonstrated high emission stability with EL spectra under different operating voltages (6–9 V) revealing an unchanged profile with a single emission band (Figure 7b), indicating the recombination zone of the excitons confined inside the EML. No emission peaks at low wavelengths from the supporting layers (NPB

• = 20%, PLQY in a thin film = 35%, and charge recombination: ηrec = 100%) to be 47%. This EUE was higher than the 25% theoretical upper limit of spin statistics for typical fluorescent emitters, indicating that the triplet excitons have been utilized via an HLCT mechanism to contribute to the EL in this

• characteristics of HLCT and weak AIE were clearly evidenced by a solvatochromic study, emission in THF/water investigation, and theoretical calculations. These synergetic properties could benefit for effective utilization of excitons in the OLED. A collaborative consequence of its D–A–D-type structure, a strong

Organic thermally activated delayed fluorescence material with strained benzoguanidine donor

• Alexander C. Brannan,
• Elvie F. P. Beaumont,
• Nguyen Le Phuoc,
• George F. S. Whitehead,
• Mikko Linnolahti and
• Alexander S. Romanov

Beilstein J. Org. Chem. 2023, 19, 1289–1298, doi:10.3762/bjoc.19.95

• : guanidine; organic; photoluminescence; TADF; yellow; Introduction Thermally activated delayed fluorescence (TADF) is a photoluminescence mechanism where excitons undergo thermally-assisted reverse-intersystem crossing from an excited triplet state to a higher-lying in energy singlet state to emit delayed

• fluorescence [1][2][3]. Organic TADF emitters have gained substantial attention in recent years for their prospective application in organic light-emitting diodes (OLEDs), photocatalysis, bioimaging, and sensors [4][5][6]. The ability to harvest both singlet and triplet excitons enable organic TADF emitters to

The effect of dark states on the intersystem crossing and thermally activated delayed fluorescence of naphthalimide-phenothiazine dyads

• Liyuan Cao,
• Xi Liu,
• Xue Zhang,
• Jianzhang Zhao,
• Fabiao Yu and
• Yan Wan

Beilstein J. Org. Chem. 2023, 19, 1028–1046, doi:10.3762/bjoc.19.79

• harvesting efficiency of both the singlet and triplet excitons and thus a high quantum efficiency for the electroluminescence [13]. The TADF emission process involves the reverse intersystem crossing (rISC) from the triplet (T1) state to the emissive singlet (S1) state. A typical molecular structure motif

Ionic multiresonant thermally activated delayed fluorescence emitters for light emitting electrochemical cells

• Merve Karaman,
• Abhishek Kumar Gupta,
• Subeesh Madayanad Suresh,
• Tomas Matulaitis,
• Lorenzo Mardegan,
• Daniel Tordera,
• Henk J. Bolink,
• Sen Wu,
• Stuart Warriner,
• Ifor D. Samuel and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2022, 18, 1311–1321, doi:10.3762/bjoc.18.136

• limited to 25% [13]. Thermally activated delayed fluorescent (TADF) emitters are one class of purely organic materials that can harvest triplet excitons in electroluminescent (EL) devices through a triplet to singlet reverse intersystem crossing (RISC) upconversion process [14]. Indeed, OLEDs using TADF

Mechanochemical bottom-up synthesis of phosphorus-linked, heptazine-based carbon nitrides using sodium phosphide

• Blaine G. Fiss,
• Georgia Douglas,
• Michael Ferguson,
• Jorge Becerra,
• Jesus Valdez,
• Trong-On Do,
• Tomislav Friščić and
• Audrey Moores

Beilstein J. Org. Chem. 2022, 18, 1203–1209, doi:10.3762/bjoc.18.125

• notable in absorption for g-h-PCN300 (Figure S5b, teal). This reduction in photoluminescence has previously been reported for phosphorus-doped carbons and carbon nitrides [52], as the addition of Lewis basic heteroatoms improves the stability of excitons, slowing the rate of recombination. Time-resolved

Synthesis, optical and electrochemical properties of (D–π)₂-type and (D–π)₂Ph-type fluorescent dyes

• Kosuke Takemura,
• Kazuki Ohira,
• Taiki Higashino,
• Keiichi Imato and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2022, 18, 1047–1054, doi:10.3762/bjoc.18.106

• intermolecular π–π interactions between the fluorophores leading to delocalization of excitons or excimers in the solid state would be responsible for the bathochromic shifts of λmax,abs and λmax,fl and lowering of Φfl with change of state from solution to solid [34][35][36]. The τfl-solid values of OTK-2 and

Post-synthesis from Lewis acid–base interaction: an alternative way to generate light and harvest triplet excitons

• Hengjia Liu and
• Guohua Xie

Beilstein J. Org. Chem. 2022, 18, 825–836, doi:10.3762/bjoc.18.83

• intermolecular mechanism, considered as post-synthesis of new luminescent compounds offers promising applications in sensing and electroluminescence by manipulating the frontier molecular orbital energy levels of organic conjugated materials, simply based on Lewis acid–base chemistry. Keywords: excitons

• are fluorescent compounds. Based on the spin statistics, the fluorescent emitters can only use singlet excitons for light generation [5]. In contrast, phosphorescent materials based on metal complexes could achieve a high internal quantum efficiency (IQE) up to 100% through intersystem crossing (ISC

• , delayed fluorescence profiles of the exciplexes were detected (see Figure 12c, τ1 = 57.07 ns and τ2 = 158.20 ns), which proved the possibility to harvest triplet excitons based on Lewis acid–base adducts. Therefore, the OLED using 35DCzPPy:B(C6F5)3 as the emitting layer exhibited a maximum external

Effect of a twin-emitter design strategy on a previously reported thermally activated delayed fluorescence organic light-emitting diode

• Ettore Crovini,
• Zhen Zhang,
• Yu Kusakabe,
• Yongxia Ren,
• Yoshimasa Wada,
• Bilal A. Naqvi,
• Prakhar Sahay,
• Tomas Matulaitis,
• Stefan Diesing,
• Ifor D. W. Samuel,
• Wolfgang Brütting,
• Katsuaki Suzuki,
• Hironori Kaji,
• Stefan Bräse and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 2894–2905, doi:10.3762/bjoc.17.197

• luminescence in an OLED is achieved through the radiative decay of electrically generated excitons, high-efficiency devices must be able to harvest both the 25% singlet and 75% triplet excitons to produce light [3]. Distinct from phosphorescent compounds, TADF molecules harvest triplet excitons by converting

• PEDOT:PSS to the emitting layer. Besides, PVK and PPF, possessing high T1 energies of 3.0 eV [41] and 3.1 eV [42], respectively, were inserted to confine the excitons in the emitting layer. PEDOT:PSS, PVK and the emitting layer were fabricated by spin-coating, and the other layers were vacuum-deposited

Exploring the possibility of using fluorine-involved non-conjugated electron-withdrawing groups for thermally activated delayed fluorescence emitters by TD-DFT calculation

• Dongyang Chen and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 210–223, doi:10.3762/bjoc.17.21

• ) materials have generated significant attention recently, particularly for their use as emitters in organic light-emitting diodes (OLEDs). This is due to their ability to utilize both singlet excitons and triplet excitons, thereby increasing the theoretical internal quantum efficiency (IQE) to 100% from 25

• % for fluorescent compounds [1][2][3][4]. For TADF materials, a small energy gap between the lowest singlet and triplet excited states (ΔEST) is essential to permit the efficient up-conversion of triplet excitons to singlet excitons via reverse intersystem crossing (rISC) [5][6][7]. The rISC process can

Control over size, shape, and photonics of self-assembled organic nanocrystals

• Chen Shahar,
• Yaron Tidhar,
• Yunmin Jung,
• Haim Weissman,
• Sidney R. Cohen,
• Ronit Bitton,
• Iddo Pinkas,
• Gilad Haran and
• Boris Rybtchinski

Beilstein J. Org. Chem. 2021, 17, 42–51, doi:10.3762/bjoc.17.5

• of the exciton–exciton annihilation process, occurring when a high photon flux results in multiple excitons, which can efficiently diffuse through the aggregated material, resulting in exciton annihilation [51]. In order to validate the observed behavior and prove that the measured differences

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

• Dominik Göbel,
• Marius Friedrich,
• Enno Lork and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2020, 16, 1683–1692, doi:10.3762/bjoc.16.139

• can occur. While the latter decay (fluorescence) takes place without a change in the electron spin, phosphorescence is defined as the radiative transition from the lowest excited triplet state (T1) to the singlet ground state (S0) [18][19][20][21]. Triplet state excitons are generated by the spin

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• material is drastically different for inorganic and organic semiconductors. High εr(ω) materials, such as silicon (εr(ω) = 12) or GaAs (εr(ω) = 13), effectively screen the Coulombic attraction between excitons to 10s of meV, allowing the charge carriers to easily dissociate at room temperature [109][110

• ]. Organic polymer materials, such poly(p-phenylene vinylene, εr(ω) = 2), typically have low εr(ω) values, which prevents the screening of excitons and leads to much stronger binding energies of 0.1–1 eV, which greatly exceeds the available thermal energy at room temperature [111][112][113]. This is

• of the photogenerated excitons is normally only a few nm3 and accounts for the large binding energy, as opposed to in a Si crystal, which has an exciton diameter in the order of 10s of nm3 [115]. Organic molecules will typically have large geometric relaxations to cope with the localised loss of

Development of fluorinated benzils and bisbenzils as room-temperature phosphorescent molecules

• Shigeyuki Yamada,
• Takuya Higashida,
• Yizhou Wang,
• Masato Morita,
• Takuya Hosokai,
• Kaveendra Maduwantha,
• Kaveenga Rasika Koswattage and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 1154–1162, doi:10.3762/bjoc.16.102

• intersystem crossing (ISC), resulting in the emission of phosphorescence [9]. Phosphorescent molecules generate two excitons (i.e., 25% S1 excitons and 75% T1 excitons) by application of an electric field, which is well known for organic light-emitting diodes. S1 excitons are converted to T1 excitons via an

Aryl-substituted acridanes as hosts for TADF-based OLEDs

• Naveen Masimukku,
• Dalius Gudeika,
• Oleksandr Bezvikonnyi,
• Ihor Syvorotka,
• Rasa Keruckiene,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 989–1000, doi:10.3762/bjoc.16.88

• , high singlet and triplet energies (higher than those of the guest) are required for host compounds for qualifying host–guest energy transfer, thus implying restrict of the emissive excitons on the TADF emitters [11]. High glass-transition temperatures are also required for increasing the morphological

Synthesis and optoelectronic properties of benzoquinone-based donor–acceptor compounds

• Daniel R. Sutherland,
• Nidhi Sharma,
• Georgina M. Rosair,
• Ifor D. W. Samuel,
• Ai-Lan Lee and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2019, 15, 2914–2921, doi:10.3762/bjoc.15.285

• . This is possible as these compounds possess very small exchange energies between their excited singlet and triplet states (ΔEST), which facilitates reverse intersystem crossing (RISC), in which singlet excitons are generated from triplet excitons. In order to obtain a small ΔEST, the molecular design

• ps [40], with efficiency close to unity [41][42], implying that the nonradiative ISC channel of excitons from S1 to T1 is always preferred over the radiative decay from the S1 state. For compound 3, we observed a prompt lifetime of 19.4 ns, which indicated there was not ultrafast ISC. This is

Synthesis, photophysical and electrochemical properties of pyridine, pyrazine and triazine-based (D–π–)₂A fluorescent dyes

• Keiichi Imato,
• Toshiaki Enoki,
• Koji Uenaka and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2019, 15, 1712–1721, doi:10.3762/bjoc.15.167

• known that D–π–A fluorescent dyes show bathochromic shifts of the λmax,fl and lower Φf values by changing from the solution state to the solid state. This fact is attributed to the delocalization of excitons or excimers due to the formation of intermolecular π–π interactions [48][49][50][51] between the

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• phosphorescent organic light-emitting diodes (PhOLEDs) and light-emitting electrochemical cells (LEECs). This interest is driven by the fact that luminescent TMCs with long-lived excited state lifetimes are able to efficiently harvest both singlet and triplet electro-generated excitons, thus opening the

• electrophosphorescent devices, the triplet nature of excited states localized on the active TMCs allows harvesting of both singlet and triplet electro-generated excitons through either direct trapping or energy transfer processes. As a consequence, the theoretical internal quantum efficiency rises from 25%, which

Two novel blue phosphorescent host materials containing phenothiazine-5,5-dioxide structure derivatives

• Feng-Ming Xie,
• Qingdong Ou,
• Qiang Zhang,
• Jiang-Kun Zhang,
• Guo-Liang Dai,
• Xin Zhao and
• Huai-Xin Wei

Beilstein J. Org. Chem. 2018, 14, 869–874, doi:10.3762/bjoc.14.73

• (≥170°), fast response (1 μs scale), high luminous efficiency, low drive voltage (3–10 V), thickness (less than 2 mm), lightweightness and flexibility [2][3][4][5][6]. Compared with traditional fluorescence OLEDs which only utilize singlet (25%) excitons for electroluminescence, PhOLEDs can

• simultaneously harvest both the singlet and triplet (75%) excitons through spin-orbit coupling (SOC), and obtain nearly 100% of the internal quantum efficiency (IQE). Thus, most of researchers have focused on phosphorescent organic light-emitting diodes (PhOLEDs) all over the world [7][8]. With the deepening of

D–A–D-type orange-light emitting thermally activated delayed fluorescence (TADF) materials based on a fluorenone unit: simulation, photoluminescence and electroluminescence studies

• Lin Gan,
• Xianglong Li,
• Xinyi Cai,
• Kunkun Liu,
• Wei Li and
• Shi-Jian Su

Beilstein J. Org. Chem. 2018, 14, 672–681, doi:10.3762/bjoc.14.55

• previously limited by the statistic rule of spin multiplicity. For conventional fluorescent materials, only singlet excitons are involved in electroluminescence, leading to a theoretical maximal internal quantum efficiency (IQEmax) of 25% and a theoretical maximal external quantum efficiency (EQEmax) of 5

• %, when assuming the out-coupling efficiency to be 20%. On the other hand, phosphorescent materials could utilize triplet excitons in electroluminescence processes to achieve 100% IQEmax [2][3]. However, the utilization of metals like iridium and platinum, which are expensive and nonrenewable, inevitably

• increase the cost of the final OLEDs. Alternatively, a thermally activated delayed fluorescence (TADF) material is a kind of noble-metal-free fluorescent material able to transform triplet excitons into singlet excitons through reverse intersystem crossing (RISC) to achieve 100% IQEmax in theory [4]. On the

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

• singlet excited states by reverse intersystem crossing (RISC). By harvesting both singlet and triplet excitons for light emission, OLEDs competing and sometimes overcoming the performance of phosphorescence-based OLEDs could be fabricated, justifying the interest for this new family of materials massively

• the light-emitting ability of the emitter, which is directly related to the nature, and the photoluminescence quantum yield (PLQY) of the emitter. Based on spin statistics, upon electrical excitation, singlet and triplet excitons are formed in a 1:3 ratio [4]. In the case of fluorescent materials

• , only singlet excitons can be utilized for light emission, limiting the internal quantum efficiency (IQE) of fluorescent OLEDs to 25%. Conversely, phosphorescent materials can both harvest singlet and triplet excitons for emission by intersystem crossing (ISC), enabling to reach a theoretical IQE of 100

Molecular-level architectural design using benzothiadiazole-based polymers for photovoltaic applications

• Vinila N. Viswanathan,
• Arun D. Rao,
• Upendra K. Pandey,
• Arul Varman Kesavan and
• Praveen C. Ramamurthy

Beilstein J. Org. Chem. 2017, 13, 863–873, doi:10.3762/bjoc.13.87

• parameters to consider for the design of a new donor polymer system. In OPV devices, a bicontinuous layer of a donor and an acceptor material is sandwiched between two electrodes. After the absorption of light, excitons are generated which dissociate towards the interface of the donor–acceptor layer and are

Synthesis and chemosensing properties of cinnoline-containing poly(arylene ethynylene)s

• Natalia A. Danilkina,
• Petr S. Vlasov,
• Semen M. Vodianik,
• Andrey A. Kruchinin,
• Yuri G. Vlasov and
• Irina A. Balova

Beilstein J. Org. Chem. 2015, 11, 373–384, doi:10.3762/bjoc.11.43

• completely quenches the fluorescence of the whole polymer chain, giving the increase of the sensitivity (amplification). This effect is also known as superquenching and comes from the delocalization of the charge carriers in the polymeric structures. Transport of excitons along the polymer backbone in a

• separate molecule as well as the transport of excitons between adjacent molecules makes possible a non-radiative relaxation of many excitons at a single trap created as a result of an analyte binding to a receptor integrated into the polymer chain [10]. As long as the trap and the generation sites of the

• exciton are spatially separated, the quenching amplification factor is only limited by the diffusion distance of the exciton. In practice, a single bound analyte molecule can deactivate excitons within 130 neighboring phenylene ethynylene repeating units [4]. Sensors based on CPs can be classified either

Studies on the photodegradation of red, green and blue phosphorescent OLED emitters

• Susanna Schmidbauer,
• Andreas Hohenleutner and
• Burkhard König

Beilstein J. Org. Chem. 2013, 9, 2088–2096, doi:10.3762/bjoc.9.245

• . While fluorescent dyes normally emit from their singlet excited states (at room temperature) and therefore can only utilize singlet excitons, phosphorescent organotransition metal dopants emit from their triplet excited states. In addition phosphorescent organotransition metal dopants are able to

• effectively convert singlet into triplet states via fast intersystem crossing. The recombination of electron–hole pairs generates singlet and triplet excitons in a ratio of 1:3 which means that the use of phosphorescent devices can give up to 4 times higher efficiencies than those based on fluorescent