Visible-light-excited robust room-temperature phosphorescence of dimeric single-component luminophores in the amorphous state.

Organic room temperature phosphorescence (RTP) has significant potential in various applications of information storage, anti-counterfeiting, and bio-imaging. However, achieving robust organic RTP emission of the single-component system is challenging to overcome the restriction of the crystalline state or other rigid environments with cautious treatment. Herein, we report a single-component system with robust persistent RTP emission in various aggregated forms, such as crystal, fine powder, and even amorphous states. Our experimental data reveal that the vigorous RTP emissions rely on their tight dimers based on strong and large-overlap π-π interactions between polycyclic aromatic hydrocarbon (PAH) groups. The dimer structure can offer not only excitons in low energy levels for visible-light excited red long-lived RTP but also suppression of the nonradiative decays even in an amorphous state for good resistance of RTP to heat (up to 70 °C) or water. Furthermore, we demonstrate the water-dispersible nanoparticle with persistent RTP over 600 nm and a lifetime of 0.22 s for visible-light excited cellular and in-vivo imaging, prepared through the common microemulsion approach without overcaution for nanocrystal formation.

Stable and ultralong room-temperature phosphorescent copolymers with excellent adhesion, resistance, and toughness.

Developing stable room-temperature phosphorescence (RTP) emission without being affected by moisture and mechanical force remains a great challenge for purely organic systems, due to their triplet states sensitive to the infinitesimal motion of phosphors and the oxygen quencher. We report a kind of highly robust phosphorescent systems, by doping a rigid phosphor into a copolymer (polyvinyl butyral resin) matrix with a balance of mutually exclusive features, including a rigidly hydrophilic hydrogen bond network and elastically hydrophobic constituent. Impressively, these RTP polymeric films have superior adhesive ability on various surfaces and showed reversible photoactivated RTP with lifetimes up to 5.82 seconds, which can be used as in situ modulated anticounterfeit labels. They can maintain a bright afterglow for over 25.0 seconds under various practical conditions, such as storage in refrigerators, soaking in natural water for a month, or even being subjected to strong collisions and impacts. These findings provide deep insights for developing stable ultralong RTP materials with desirable comprehensive performance.

Achieving Record External Quantum Efficiency of 11.5% in Solution-Processable Deep-Blue Organic Light-Emitting Diodes Utilizing Hot Exciton Mechanism.

High performance solution-processable deep-blue emitters with a Commission International de l'Eclairage (CIE) coordinate of CIEy ≤ 0.08 are highly desired in ultrahigh-definition display. Although, deep-blue materials with hybridized local and charge-transfer (HLCT) excited-state feature are promising candidates, their rigidity and planar molecular structures limit their application in solution-processing technique. Herein, four novel deep-blue solution-processable HLCT emitters were first proposed by attaching rigid imide aliphatic rings as functional units onto the HLCT emitting core. The functional units not only improve solubility, enhance thermal properties and morphological stability of the emitting core, but also promote photoluminescence efficiency, balance charge carrier transport, and inhibit aggregation-caused quenching effect due to the weak electron-withdrawing property as well as steric hindrance. The corresponding solution-processable organic light-emitting diodes (OLEDs) substantiate an unprecedented maximum external quantum efficiency (EQEmax) of 11.5% with an emission peak at 456 nm and excellent colour purity (full width at half maximum = 56 nm and CIEy = 0.09). These efficiencies represent the state-of-the-art device performance among the solution-processable blue OLEDs based on the "hot exciton" mechanism. This simple strategy opens up a new avenue for designing highly efficient solution-processable deep-blue organic luminescent materials.

Enabling Highly Robust Full-Color Ultralong Room-Temperature Phosphorescence and Stable White Organic Afterglow from Polycyclic Aromatic Hydrocarbons.

In this work, full-color and stable white organic afterglow materials with outstanding water, organic solvents, and temperature resistances have been developed for the first time by embedding the selected polycyclic aromatic hydrocarbons into melamine-formaldehyde polymer via solution polymerization. The afterglow quantum yields and lifetimes of the resulting polymer films were up to 22.7 % and 4.83 s, respectively, under ambient conditions. For the coronene-doped sample, its afterglow color could be linearly tuned between yellow and blue by adjusting the temperature, and it could still emit an intense blue afterglow with a lifetime of 0.68 s at 440 K. Moreover, the films showed a bright and stable white afterglow at 370 K with a lifetime of 2.80 s and maintained an excellent afterglow performance after soaking in water and organic solvents for more than 150 days. In addition, the application potential of the polymer films in information encryption and anti-counterfeiting was also demonstrated.

Dynamic Ultra-long Room Temperature Phosphorescence Enabled by Amorphous Molecular "Triplet Exciton Pump" for Encryption with Temporospatial Resolution.

Organic ultra-long room-temperature phosphorescence (RTP) materials in the amorphous state have attracted widespread attention due to their simple preparation and flexibility to adopt various forms in sensors, bioimaging, and encryption applications. However, the amorphous molecular host for the host-guest RTP systems is highly demanded but limited. Here, a universal molecular host (DPOBP-Br) has been designed by integration of an amorphous moiety of diphenylphosphine oxide (DPO) and an intersystem crossing (ISC) group of 4-bromo-benzophenone (BP-Br). Various commercial fluorescence dyes were doped into the tight and transparent DPOBP-Br film, respectively, resulting in amorphous host-guest systems with ultra-long RTP colors from green to red. It was found that DPOBP-Br acted as a universal "triplet exciton pump" for promoting the generation of triplet excitons in the guest, through energy transfer processes and external heavy-atom effect based on DPOBP-Br. Interestingly, dynamic RTP was achieved by controlling residual oxygen concentration in the amorphous matrix by UV irradiation. Therefore, multi-dimensional anti-counterfeiting coatings were realized even on curved surfaces, simultaneously exhibiting spatial and 2D-time dependence. This work provides a strategy to design new amorphous molecular hosts for RTP systems and demonstrates the advanced information encryption with tempo-spatial resolution based on the dynamic ultra-long RTP of an amorphous system.

Ultralow Coefficient of Thermal Expansion and a High Colorless Transparent Polyimide Film Realized Through a Reinforced Hydrogen-Bond Network by In Situ Polymerization of Aromatic Polyamide in Colorless Polyimide.

Colorless polyimides (CPIs) are a key substrate material for flexible organic light-emitting diode (OLED) displays and have attracted worldwide attention. Here, in this paper, the dispersion and interfacial interaction of aromatic polyamide (PA) in CPI (synthesized from 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 2,2'-bis(trifluoromethyl)benzidine (TFMB)) were significantly improved by in situ polymerization, and colorless transparent macromolecular polyimide composites (CPI-PAx) were successfully prepared by PA and CPI. By adjusting the ratio of PA to CPI, a high-performance engineering plastic with excellent film-forming properties was obtained. Molecular simulations confirmed the uniform distribution of PA in CPI and its interaction in polymers. In CPI-PAx, the CPI was locked by the PA chain, and numerous molecular chains were mutually entangled to form a hydrogen-bond network structure. Due to the strong interaction between the chains imparted by the hydrogen bonds of the PA, they do not slide under external forces and heating. In addition, the additive PA has excellent dimensional stability, thermal, and mechanical properties, and CPI has outstanding optical properties, so the synthesized CPI-PAx combines the comprehensive properties of PA and CPI. The CPI-PAx has excellent thermal and mechanical properties, with a thermal decomposition temperature of 499 °C, a glass transition temperature of 385 °C, a coefficient of thermal expansion of 0.8 ppm K-1, a tensile strength of 50.9 MPa, and an elastic modulus of 3.9 GPa. Particularly, CPI-PAx has a 90% transmittance in the visible region. These data prove that the strategy of combining PA and CPI by in situ polymerization is an effective method to circumvent the bottleneck of CPI in the current flexible window application, and this design strategy is universal.

Synergetic Conformational Regulations in Ground and Excited States for Realizing Stimulus-Responsive and Wide-Tuning Room-Temperature Phosphorescence.

Understanding the changes of molecular conformations is crucial for realizing multiple emissive triplet states in room-temperature phosphorescence (RTP) materials. In this work, we report two molecules, 4,4'-dimethylbenzil (DMBZ) and 4,4'-di-tert-butylbenzil (DBBZ) with conformation-dependent luminescence, and demonstrate that stimulus-responsive and wide-tuning RTP emissions can be realized via synergetic conformational regulations in ground and excited states. Due to conformational changes, DMBZ and DBBZ show abundant RTP variations upon external stimuli, including light, force, heat, and fumigation. Notably, DBBZ exhibits multiple conformational changes in both ground and excited states, which endow DBBZ with multiple emissive states and unique stimulus-responsive behaviors. DBBZ presents multiple phase transitions between the supercooled liquid state and different solid states accompanied by different phosphorescence transitions, in which the excited-state conformations are effectively regulated. Moreover, wide-range RTP regulations (between cyan, green, and yellow) are realized in both single component and host-guest systems of DBBZ, showing potential applications in temperature sensing, multicolor dynamic displays, and information encryption. These results may provide new visions for understanding the complicated conformational changes in the aggregated state, as well as unique insights into the relationship between molecular conformations, RTP emissions, and stimulus responsiveness.

Multistimuli-responsive fluorescence behaviours of aggregation-induced emission small-molecule and electrospun nanofibre films for acid-base vapour sensing.

Multistimuli-responsive fluorescent materials have garnered great research interest benefited from their practical applications. Two twisted-structure compounds containing tetraphenylethylene (TPE) as the aggregation-induced emission (AIE) group and a pyridine unit as the acid reaction site to obtain new multistimuli-responsive fluorescent compounds (namely, TPECNPy: TPECNPy-2 and TPECNPy-3) were successfully synthesized through a one-step Knoevenagel condensation reaction. The multiple-stimuli response process of TPECNPy was investigated by means of photoluminescence (PL) spectra and emission colour. The results showed that both TPECNPy compounds with excellent AIE abilities displayed reversible emission wavelength and colour changes in response to multiple external stimuli, including grinding-fuming by CH2 Cl2 or annealing and HCl-NH3 vapour fuming. More importantly, fluorescent nanofibre films were prepared by electrospinning a solution of TPECNPy mixed with cellulose acetate (CA), and these exhibited reversible acid-induced discolouration, even with only 1 wt% TPECNPy. The results of this study may inspire strategies for designing multistimuli-responsive materials and preparing fluorescent sensing nanofibre films.

How Matrixes Influence Room Temperature Ultralong Organic Phosphorescence: 4-Dimethylaminopyridine vs Carbazole Derivative.

How matrixes influence room temperature ultralong organic phosphorescence (RTUOP) in the doping systems is a fundamental question. In this study, we construct guest-matrix doping phosphorescence systems by using the derivatives (ISO2N-2, ISO2BCz-1, and ISO2BCz-2) of three phosphorescence units (N-2, BCz-1, and BCz-2) and two matrixes (ISO2Cz and DMAP) and systematically investigate their RTUOP properties. Firstly, the intrinsic phosphorescence properties of three guest molecules were studied in solution, in the pure powder state, and in PMMA film. Then, the guest molecules were doped into the two matrixes with increasing weight ratio. To our surprise, all of the doping systems in DMAP feature a longer lifetime but weaker phosphorescence intensity, while all of the doping systems in ISO2Cz exhibit a shorter lifetime but higher phosphorescence intensity. According to the single-crystal analysis of the two matrixes, resemblant chemical structures of the guests and ISO2Cz enable them to approach each other and interact with each other via a variety of interactions, thus facilitating the occurrence of charge separation (CS) and charge recombination (CR). The HOMO-LUMO energy levels of the guests match well with the ones of ISO2Cz, which also significantly promotes the efficiency of the CS and CR process. To our best knowledge, this work is a systematic study on how matrixes influence the RTUOP of guest-matrix doping systems and may give deep insight into the development of organic phosphorescence.

Selenium-Containing Type-I Organic Photosensitizers with Dual Reactive Oxygen Species of Superoxide and Hydroxyl Radicals as Switch-Hitter for Photodynamic Therapy.

Organic type-I photosensitizers (PSs) which produce aggressive reactive oxygen species (ROS) with less oxygen-dependent exhibit attractive curative effect for photodynamic therapy (PDT), as they adapt better to hypoxia microenvironment in tumors. However, the reported type-I PSs are limited and its exacted mechanism of oxygen dependence is still unclear. Herein, new selenium-containing type-I PSs of Se6 and Se5 with benzoselenadiazole acceptor has been designed and possessed aggregation-induced emission characteristic. Benefited from double heavy-atom-effect of selenium and bromine, Se6 shows a smaller energy gap (ΔEST ) of 0.03 eV and improves ROS efficiency. Interestingly, type-I radicals of both long-lived superoxide anion (O2 •‾ ) and short-lived hydroxyl (• OH) are generated from them upon irradiation. This may provide a switch-hitter of dual-radical with complementary lifetimes for PDT. More importantly, simultaneous processes to produce • OH are revealed, including disproportionation of O2 •‾ and reaction between excited PS and water. Actually, Se6 displays superior in-vitro PDT performance to commercial chlorin e6 (Ce6), under normoxia or hypoxia. After intravenous injection, a significantly in-vivo PDT performance is demonstrated on Se6, where tumor growth inhibition rates of 99% is higher than Ce6. These findings offer new insights about both molecular design and mechanism study of type-I PSs.

Grafting Polyethyleneimine-Poly(ethylene glycol) Gel onto a Heat-Resistant Polyimide Nanofiber Separator for Improving Lithium-Ion Transporting Ability in Lithium-Ion Batteries.

To improve the lithium-ion transporting ability in lithium-ion batteries, a high-performance polyimide-based lithium-ion battery separator (PI-mod) was prepared by chemically grafting poly(ethylene glycol) (PEG) onto the surface of a heat-resistant polyimide nanofiber matrix with the assistance of amino-rich polyethyleneimine (PEI). The resulted PEI-PEG polymer coating exhibited unique gel-like properties with an electrolyte uptake rate of 168%, an area resistance as low as 2.60 Ω·cm2, and an ionic conductivity up to 2.33 mS·cm-1, which are 3.5, 0.10, and 12.3 times that of the commercial separator Celgard 2320, respectively. Meanwhile, the heat-resistant polyimide skeleton can effectively avoid thermal shrinkage of the modified separator even after 200 °C treatment for 0.5 h, which ensures the safety of the battery working under extreme conditions. The modified PI separator possessed a high electrochemical stability window of 4.5 V. Compared with the batteries from the commercial separator Celgard 2320 and the pure polyimide matrix, the assembled coin cell with the PI-mod separator showed much better rate capabilities and capacity retention due to the high electrolyte affinity of the PEI-PEG polymer coating. The developed strategy of using the electrolyte-swollen polymer to modify the thermal-resistant separator network provides an efficient way for establishing high-power lithium-ion batteries with good safety performance.

Y-Shaped D-A Type Thioxanthone Derivatives: Mechano-Induced Thermally Activated Delayed Fluorescence and High-Contrast Mechano-Responsive Luminescence.

High-contrast mechano-responsive luminescence (MRL) materials with mechano-induced emission enhancement properties are fascinating candidates but few, for applications in rewritable media and recording devices. Here, an interesting design strategy of "Y-shape" donor-acceptor (D-A) type molecules for high-contrast MRL materials was presented, based on substituted diphenylamine donor and planar acceptor. Interestingly, their D-A torsion angles are small in crystals but increased after ground, resulted in planar and twist intramolecular charge transfer (PICT and TICT) states, respectively. Therefore, high-contrast MRL switching between weak blue (450 nm) fluorescence and bright yellow (552 nm) thermally activated delayed fluorescence (TADF) can be achieved for compound TXDO (4,4'-dimethoxydiphenylamine donor), which photoluminescence quantum yield increased from 2.8 % to 54.7 % after ground. Most importantly, the two independent D-A conjugation dihedral angles are actually independent in the "Y-shape" molecules. Especially for compound TXDT (4,4'-di-tert-butyldiphenylamine donor), its crystal exhibited both PICT and TICT processes inside, resulted from the different dihedral angles of 11.8° and 35.5°, respectively. The TXDT crystal thus showed dual-peak emission, including both TICT fluorescence and PICT room-temperature phosphorescence. Therefore, this strategy of "Y-shape" D-A type molecules provide a new approach to design advanced luminescent materials with mechano-induced TADF feature, for high-contrast MRL and single-component white luminescence.

Photoinduced Radical Persistent Luminescence in Semialiphatic Polyimide System with Temperature and Humidity Resistance.

Organic persistent luminescence (pL) systems with photoresponsive dynamic features have valuable applications in the fields of data encryption, anticounterfeiting, and bioimaging. Photoinduced radical luminescent materials have a unique luminous mechanism with the potential to achieve dynamic pL. It is extremely challenging to obtain radical pL under ambient conditions; on account of it, it is unstable in air. Herein, a new semialiphatic polyimide-based polymer (A0) is developed, which can achieve dynamic pL through reversible conversion of radical under photoexcitation. A "joint-donor-spacer-acceptor" molecular design strategy is applied to effectively modulate the intramolecular charge-transfer and charge-transfer complex interactions, resulting in effective protection of the radical generated under photoirradiation. Meanwhile, polyimide-based polymers of A1-A4 are obtained by doping different amine-containing fluorescent dyes to modulate the dynamic afterglow color from green to red via the triplet to singlet Förster resonance energy-transfer pathway. Notably, benefiting from the structural characteristics of the polyimide-based polymer, A0-A4 have excellent processability, thermal stability, and mechanical properties and can be applied directly in extreme environments such as high temperatures and humidity.

Benzoxazole-Based Hybridized Local and Charge-Transfer Deep-Blue Emitters for Solution-Processable Organic Light-Emitting Diodes and the In fluences of Hexahydrophthalimido.

Hybridized local and charge-transfer (HLCT) emitters have attracted extensive attention, but the insolubility and severe self-aggregation tendency restrict their applications in solution-processable organic light-emitting diodes (OLEDs), particularly deep-blue OLEDs. Herein, two novel benzoxazole-based solution-processable HLCT emitters (BPCP and BPCPCHY) are designed and synthesized, in which benzoxazole acts as an acceptor, carbazole acts as a donor, and hexahydrophthalimido (HP, with a large intramolecular torsion angle and spatial distortion characteristics) acts as a bulky modified end-group with weak electron-withdrawing effects. Both BPCP and BPCPCHY exhibit HLCT characteristics and emit near ultraviolet in toluene at 404 and 399 nm. Compared to the BPCP, the BPCPCHY solid shows much better thermal stability (Tg, 187 vs 110 °C), higher oscillator strengths of the S1-to-S0 transition (0.5346 vs 0.4809), and faster kr (1.1 × 108 vs 7.5 × 107 s-1) and thus a much higher ΦPL in the neat film. The introduction of HP groups greatly suppresses the intra-/intermolecular charge-transfer effect and self-aggregation trends, and the BPCPCHY neat films placed in air for 3 months can still maintain an excellent amorphous morphology. The solution-processable deep-blue OLEDs utilizing BPCP and BPCPCHY achieved a CIEy of 0.06 with maximum external quantum efficiency (EQEmax) values of 7.19 and 8.53%, respectively, which are among the best results of the solution-processable deep-blue OLEDs based on the "hot exciton" mechanism. All of the above results indicate that benzoxazole is an excellent acceptor for constructing deep-blue HLCT materials, and the strategy of introducing HP as a modified end-group into an HLCT emitter provides a new perspective to develop solution-processable efficient deep-blue OLEDs with high morphological stability.

Isomeric thermally activated delayed fluorescence emitters for highly efficient organic light-emitting diodes.

The isomeric strategy is an important design concept in molecular design that has a non-negligible influence on molecular properties. Herein, two isomeric thermally activated delayed fluorescence (TADF) emitters (NTPZ and TNPZ) are constructed with the same skeleton consisting of an electron donor and electron acceptor but different connection sites. Systematic investigations show that NTPZ exhibits a small energy gap, large up-conversion efficiency, low non-radiative decay, and high photoluminescence quantum yield. Further theoretical simulations reveal that the excited molecular vibrations play a key role in regulating the non-radiative decays of the isomers. Therefore, an NTPZ based OLED achieves better electroluminescence performances, such as a higher external quantum efficiency of 27.5% compared to a TNPZ based OLED (18.3%). This isomeric strategy not only provides an opportunity to deeply understand the relationship between substituent locations and molecular properties, but also affords a simple and effective strategy to enrich TADF materials.

Color-Tunable Dual-Mode Organic Afterglow from Classical Aggregation-Caused Quenching Compounds for White-Light-Manipulated Anti-Counterfeiting.

Color-tunable dual-mode organic afterglow excited by ultraviolet (UV) and white light was achieved from classical aggregation-caused quenching compounds for the first time. Specifically, two luminescent systems, which could produce significant organic afterglow composed of persistent thermally activated delayed fluorescence and ultralong organic phosphorescence under ambient conditions, were constructed by doping fluorescein sodium and calcein sodium into aluminum sulfate. Their lifetimes surpassed 600 ms, and the dopant concentrations were as low as 5×10-6  wt %. Moreover, the persistent luminescence colors of the materials could be tuned from blue to green and then to yellow by simply varying the concentrations of guest compounds or the temperature in the range of 260-340 K. Inspired by these exciting results, the afterglow materials were used for UV- and white-light-manipulated anti-counterfeiting and preparation of elastomers with different colors of persistent luminescence.

A dish-like molecular architecture for dynamic ultralong room-temperature phosphorescence through reversible guest accommodation.

Developing dynamic organic ultralong room-temperature phosphorescent (URTP) materials is of practical importance in various applications but remains a challenge due to the difficulty in manipulating aggregate structures. Herein, we report a dish-like molecular architecture via a bottom-up way, featuring guest-responsive dynamic URTP. Through controlling local fragment motions in the molecular architecture, fascinating dynamic URTP performances can be achieved in response to reversible accommodation of various guests, including solvents, alkyl bromides and even carbon dioxide. Large-scale regulations of phosphorescence lifetime (100-fold) and intensity (10-fold) can be realized, presenting a maximum phosphorescence efficiency and lifetime of 78.8% and 483.1 ms, respectively. Moreover, such a dish-like molecular architecture is employed for temperature-dependent multiple information encryption and visual identification of linear alkyl bromides. This work can not only deepen our understanding to construct multifunctional organic aggregates, but also facilitate the design of high-performance dynamic URTP materials and enrich their practical applications.

Temperature-Resistant Intrinsic High Dielectric Constant Polyimides: More Flexibility of the Dipoles, Larger Permittivity of the Materials.

High dielectric constant polymers have been widely studied and concerned in modern industry, and the induction of polar groups has been confirmed to be effective for high permittivity. However, the way of connection of polar groups with the polymer backbone and the mechanism of their effect on the dielectric properties are unclear and rarely reported. In this study, three polyimides (C0-SPI, C1-SPI, and C2-SPI) with the same rigid backbone and different linking groups to the dipoles were designed and synthesized. With their rigid structure, all of the polyimides show excellent thermal stability. With the increase in the flexibility of linking groups, the dielectric constant of C0-SPI, C1-SPI, and C2-SPI enhanced in turn, showing values of 5.6, 6.0, and 6.5 at 100 Hz, respectively. Further studies have shown that the flexibility of polar groups affected the dipole polarization, which was positively related to the dielectric constant. Based on their high permittivity and high temperature resistance, the polyimides exhibited outstanding energy storage capacity even at 200 °C. This discovery reveals the behavior of the dipoles in polymers, providing an effective strategy for the design of high dielectric constant materials.

Asymmetric Thermally Activated Delayed Fluorescence Emitter for Highly Efficient Red/Near-Infrared Organic Light-Emitting Diodes.

Developing highly efficient red/near-infrared thermally activated delayed fluorescence (TADF) materials is of great importance for organic light-emitting diodes (OLEDs). Here, we reported an asymmetric TADF emitter (TCPQ), which exhibits a high reverse intersystem crossing rate as well as a low non-radiative rate due to molecular symmetry breaking through multiple donor substitution. The coexistence of multiple donors endows TCPQ with not only near-infrared emission but also excellent device performances. As for the TCPQ-based OLEDs, the 10 and 20 wt % doped devices exhibit outstanding external quantum efficiencies (EQEs) of 21.9 and 19.2% with red emission peaks at 612 and 642 nm, respectively. Meanwhile, the non-doped device achieves an EQE of 5.4% with an emission peak at 718 nm, showing near-infrared emission. These device efficiencies are among the best performances of red/near-infrared TADF-OLEDs, demonstrating that the asymmetry design is a potential strategy for constructing long wavelength TADF materials with high efficiency.

Structurally Resemblant Dopants Enhance Organic Room-Temperature Phosphorescence.

Doping has shown very promising potential in endowing room-temperature phosphorescence (RTP) properties of organic phosphors with minimal effort. Here, a new isomer design and doping strategy is reported that is applicable to dibenzothiophene (DBT) and its derivatives. Three isomers are synthesized to study the dopant effect on enhancing RTP of DBT derivatives. It is found that isomer dopants bearing close resemblance to the host with matched highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels and small energy difference between singlet- and triplet-excited states can yield efficient RTP for the doped system. Meanwhile, phosphorescence color from yellow to red is achieved by varying isomer dopants used for doping the DBT derivatives. This work represents an RTP enhancement strategy based on isomer design and doping to construct luminescent organic phosphors.