Abstract
Near-infrared organic light-emitting diodes are attractive for a broad range of applications, including night-time surveillance and biomedical diagnostic and imaging systems. However, obtaining high device radiance, which is necessary for many applications, and maintaining high operational stability is challenging due to the rapid efficiency roll-off at a high current density. Here we develop near-infrared organic light-emitting diodes based on an acceptor–donor–acceptor organic semiconductor with greatly suppressed singlet–triplet annihilation rate and triplet lifetime, alleviating singlet quenching by long-lived triplets, thereby enabling an ultrahigh singlet density at high electrical excitation levels. Our devices exhibit J50 values of 59.2 A cm−2, that is, the current density at which the external quantum efficiency decreases to half its peak value of 1.34%. A high external quantum efficiency is also maintained over a six orders of magnitude range of current densities, at values above 5,000 A cm−2. The devices emit with the maximum radiance beyond 2,000 W sr−1 m−2 under a continuous electrical bias and 46,700 W sr−1 m−2 in the pulsed electrical operation. The half-lifetime is 35 h for an initial radiance of 100 W sr−1 m−2. We also achieve a high electrically injected singlet density of more than 1016 cm−3 at 1,000 A cm−2, which can sustain population inversion, indicating potential for organic lasers. These results pave the way for further developments of near-infrared organic light-emitting diodes as well as offer a potential route towards electrically driven organic laser diodes.
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Data availability
The data that support the findings of this study are available from the corresponding authors upon reasonable request. Source data are provided with this paper.
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Acknowledgements
Hongbin Wu thanks the National Key Research and Development Program of China (2023YFE0208500) and the National Natural Science Foundation of China (nos. 51521002 and 52273177) for financial support. Y.X. acknowledges the National Natural Science Foundation of China (no. 52473172) for financial support. W.L. thanks the China Postdoctoral Science Foundation (no. BX20240120) for financial support. X.Z. thanks the National Natural Science Foundation of China (no. 22335001). We thank the Materials Characterization Centre, East China Normal University Multifunctional Platform for Innovation, for experiment support of the TAS measurements.
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Contributions
Hongbin Wu and Y.X. conceptualized the idea and designed the experiments. W.L. and Y.X. carried out the PL quantum yield, TRPL decay, TAS and transient EL measurements and analyses. W.L., W.D. and Y.X. fabricated the NIR OLED devices and performed the device characterization and optical absorption measurements. C.G., W.W. and Haimei Wu designed and synthesized the A–D–A-type emitter i-IEICO-4Cl. Y. Chi, L.D. and Z. Zheng designed and synthesized the narrow-bandgap triplet emitter R-CF3. W.D. analysed the J–V characteristics of the devices. X.D., Z. Zhao and W.L. conducted the phosphorescence spectroscopy. Y.X. analysed the exciton dynamics and EQE roll-off characteristics and performed the numerical simulations on exciton dynamics. W.L., J.Z. and Y.X. conducted the ASE experiments. Y.X., W.L. and Hongbin Wu wrote the initial draft of the paper, and Hongbin Wu corrected it. All authors discussed the results and commented on the paper. H.W., C.G., L.D., X.Z. and Y.Z. coordinated the work. Hongbin Wu, J.P. and Y. Cao supervised the project.
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Extended data
Extended Data Fig. 1 Chemical structure and Performance characteristics of other A-D-A type molecules used in this study.
a, The chemical structure of i-IEICO-4Cl and Y11, the ring of the central donor unit is shown in red and the ring of the terminal acceptor unit in green; b-e, Current density versus voltage (J–V) (solid), radiance versus voltage characteristics (R–V) (open) and EQE roll-off at high current densities for the OLEDs based on i-IEICO-4Cl (b & c) and Y11 (d & e).
Extended Data Fig. 2 Operation lifetime of non-doped OLEDs based on BTA3 at various current density.
The active area of the measured devices based on sapphire substrate is 0.045 mm2 (a) and on glass substrate is 4.5 mm2 (b). Stability test was performed in air with encapsulation at room temperature, under continuous operating, constant current density mode. The operating half-lifetime of devices on sapphire substrate with active an area of 0.045 mm2 at 0.1 A cm‒2, 0.2 A cm‒2, 0.5 A cm‒2, 1 A cm‒2 and 5 A cm‒2 is 210.3 h, 106.6 h, 69.1 h, 35.0 h and 3.7 h, respectively. The operating half-lifetime of devices on glass substrate with an area of 4.5 mm2 at 0.1 A cm‒2, 0.2 A cm‒2 and 1 A cm‒2 is 58.0 h, 23.2 h and 11.0 h, respectively.
Extended Data Fig. 3 The delayed fluorescence after turn-off of electrical pulses for BTA3 based OLEDs.
a, Original waveform of generator produced electrical pulse, with a repetition rate of 1 kHz and a duty ratio of 1%. b, Delayed fluorescence after turn-off of electrical pulses of 1 A cm−2 and 5 A cm−2, and calculated turn-off responses at the respective singlet densities. The delayed fluorescence after turn-off suggests that a balance between singlet decay and singlet generation can be achieved at pulsed current density is 5 A cm−2 such that the EL decay is governed by the decay of triplets (Supplementary Note 1 and Note Fig. 1). Prompt decay becomes dominant whenever the pulse current is smaller or larger than 5 A cm−2 (Supplementary Note Fig. 2), which is governed by either nanosecond singlet decay (for an electrical pulse of 1 A cm−2) or enhanced TTA due to the increase in the triplet density, respectively. The monoexponential decay of the balanced delayed fluorescence gives a triplet decay rate (\({k}_{T}\)) of (7.5 ± 2.5)×106 s−1 (triplet lifetime of 0.13 μs) (Supplementary Table 7). Fitting the delayed fluorescence at 5 A cm−2 to the modified rate equations (equation 3 and equation 4, Supplementary Note 1) yields a TTA rate (\({k}_{{TT}}\)) of (2.0 ± 1.7)×10−10 cm3 s−1.
Extended Data Fig. 4 Decay kinetics of GSB for triplet-sensitized BTA3 film excited at 380 nm.
a, Transient absorption spectra of BTA3: 20 wt% PtOEP film pumped at high intensity of 206 μJ cm‒2 with a 380 nm femtosecond laser, at different time delays. b, Decay kinetics of GSB (circles) for a triplet-sensitized BTA3 film. Transient absorption dynamics49 of a neat BTA3 film at high pump intensities suffers significantly from SSA (Supplementary Note 3). Sensitized film with 20 wt% PtOEP populating the triplet states in BTA3 via the short-range triplet–triplet Dexter energy transfer mechanism, which bypasses the strong SSA was adopted. The experimentally obtained GSB decay kinetics for the triplet sensitized film well match theoretical calculations performed with the rate equation (equation 4 in Supplementary Note 1). The best fit to the data leads to an annihilation rate of 2.0×10−10 cm3 s−1, which agrees with the value of kTT determined from the transient EL measurements.
Extended Data Fig. 5 Fourier transform photocurrent spectrum of the BTA3-based OLEDs.
EU of 26.9 meV was extracted according to Urbach’s rule α(E)=α_0 e^((E-E_g)/E_U), where α(E) is the optical absorption coefficient or EQE, EU is the Urbach energy, Eg is the optical bandgap. The low energetic disorder is important for an increased exciton diffusion length, as it corresponds to a high density of available sites within the energy transfer radius and enables more efficient exciton diffusion40. The exciton diffusion coefficient (D) be estimated from the TTA rate coefficient through a time-independent formula (see Supplementary Note 4). With the k_TT extracted from Extended Data Fig. 3 and Extended Data Fig. 4, a triplet exciton diffusion coefficient of 1.6×10−4 cm2 s−1 and a long exciton diffusion length (LD) of 50 nm were obtained. The LD of BTA3 is much longer than the typical singlet of 5–10 nm and comparable to the values typically obtained for organic single crystals50. The enhanced triplet exciton diffusion can be ascribed to strong intermolecular interactions and enhanced electron delocalization of the A–D–A molecule, which enable short-range Dexter energy transfer43.
Extended Data Fig. 6 ASE measurements using nanosecond laser.
a–g, The PL intensity of 5 wt% BTA3 (a,e), 10 wt% BTA3 (c,g) and ASE thresholds were derived based on 5 wt% BTA3 (b,f), 10 wt% BTA3 (d) with CBP and Poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) as host matrix. ASE thresholds were derived based on BTA3 with CBP and Poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) as host matrix. The films were excited by 532 nm Nd:YAG laser (Q-smart, QSM-100-20-G) with a pulse duration of 5 ns and a repetition rate of 18 Hz. The average ASE threshold is estimated to be 20 μJ cm−2, corresponding to a photo flux of 4 μJ cm−2 /ns (1.07×1013 photons/cm2 /ns). This is equivalent to current density of 6.9 kA cm−2 (4.3×1013 charges/cm2 /ns), where only one quarter of injected charges become singlet excitons.
Extended Data Fig. 7 Drift–diffusion simulation of the J–V characteristics of BTA3 OLEDs.
The grey dashed line represents the diffusion current density by Shockley diode equation \(J={J}_{0}[\exp (\frac{{qV}}{{n}_{{\rm{id}}}{k}_{{\rm{B}}}T})-1]\) with an ideality factor nid of 1.2. Analysis of the exponential incline regime in the J–V characteristics of the device confirms that trap-assisted recombination dominates the current before turn-on, while trap-free bimolecular recombination starts to dominate the J–V curve after turn-on, as revealed by the ideality factor of 1.2. The driving voltage at 1 A cm−2 is found to be approximately 5.0V, which is much lower than those for NIR phosphorescent13 (~19 V @0.5 A cm−2) and TADF15 ( ~ 6 V@0.1 A cm−2) OLEDs and comparable to that for other best reported perovskite NIR LEDs7 (~4.5 V).
Supplementary information
Supplementary Information
Supplementary Figs. 1–11, Notes 1–5, Equations (1)–(10) and Tables 1–8.
Supplementary Video 1
Demonstration of the in vivo biological imaging system using our NIR OLEDs.
Source data
Source Data Fig. 1
Source data for the absorption (Fig. 1a), PL spectra (Fig. 1a), the calculated contour diagrams of frontier molecular orbitals (Fig. 1b), DFT-calculated singlet excited-state energy and triplet excited-state energy (Fig. 1c), EL spectra (Fig. 1d), J–V characteristics, R–V characteristics (Fig. 1e) and EQE roll-off characteristics (Fig. 1f).
Source Data Fig. 2
Source data for the transient behaviour under optical and electrical excitations and simulated EQE roll-off.
Source Data Fig. 3
Source data for the ASE measurements of BTA3 and simulated singlet and triplet densities.
Source Data Extended Data Fig. 1
Source data for the performance characteristics of other A–D–A-type molecules used in this study.
Source Data Extended Data Fig. 2
Source data for the operation lifetime of the devices.
Source Data Extended Data Fig. 3
Source data for the delayed fluorescence after turn-off of electrical pulses.
Source Data Extended Data Fig. 4
Source data for the decay kinetics of GSB for the triplet-sensitized BTA3 film excited at 380 nm.
Source Data Extended Data Fig. 5
Source data for the Fourier transform photocurrent spectrum of the BTA3-based OLEDs.
Source Data Extended Data Fig. 6
Source data for the ASE measurements using a nanosecond laser.
Source Data Extended Data Fig. 7
Source data for the drift–diffusion simulation of the J–V characteristics of BTA3 OLEDs.
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Liu, W., Deng, W., Wang, W. et al. Ultrahigh-radiance near-infrared organic light-emitting diodes. Nat. Photon. 19, 650–657 (2025). https://doi.org/10.1038/s41566-025-01674-5
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DOI: https://doi.org/10.1038/s41566-025-01674-5
