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Nanoscale electroluminescence inhomogeneity and blinking in organic light-emitting diodes

Nature Photonics (2026)Cite this article

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Abstract

Charge injection, transport and recombination in thin-film organic electronic devices is predicted to be filamentary on the nanoscale owing to energetic disorder. However, direct experimental evidence of this phenomenon has remained elusive. Here we study small molecule organic light-emitting diodes using super-resolution microscopy and find that their electroluminescence is spatially non-uniform at submicrometre length scales. The local electroluminescence intensity varies by up to 30% relative to the mean and flickers stochastically on millisecond-to-second timescales. These inhomogeneities are neither observed in photoluminescence nor polycrystalline organic light-emitting diodes, and differ for the highest- and lowest-energy components of the electroluminescence spectrum. They are consistent with intrinsic nanoscale variation in the local recombination rate induced by static disorder in amorphous thin films and should be present in a range of organic light-emitting diodes and other organic optoelectronic devices. Our observations should lead to improved models of nanoscale charge transport that benefit the design and performance of organic optoelectronic devices.

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Fig. 1: EL inhomogeneity in a conventional phosphorescent OLED.
Fig. 2: Blinking behaviour and super-resolution imaging of EL hot spots.
Fig. 3: Emission energy dependence of EL intermittency.
Fig. 4: EL intermittency power spectrum.
Fig. 5: EL inhomogeneity and blinking suppression in a polycrystalline OLED.
Fig. 6: Mechanism for EL inhomogeneity and blinking.

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Data availability

The data that support the findings of this study are available from either of the corresponding authors upon request.

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Acknowledgements

This work was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under award number DE-SC0024142 (J.D.S. and N.C.G. for experimental design, microscopy measurements and analysis) and by Universal Display Corporation (S.R.F.).

Author information

Authors and Affiliations

  1. Department of Electrical and Computer Engineering, University of Michigan, Ann Arbor, MI, USA

    Joshua D. Springsteen, Noel C. Giebink & Stephen R. Forrest

  2. Department of Physics, University of Michigan, Ann Arbor, MI, USA

    Noel C. Giebink & Stephen R. Forrest

  3. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA

    Stephen R. Forrest

Authors
  1. Joshua D. Springsteen
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  2. Noel C. Giebink
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  3. Stephen R. Forrest
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Contributions

J.D.S. fabricated and imaged all the devices. J.D.S., N.C.G. and S.R.F. analysed the data, and N.C.G. and S.R.F. supervised the project. J.D.S., N.C.G. and S.R.F. wrote and revised the manuscript.

Corresponding authors

Correspondence to Noel C. Giebink or Stephen R. Forrest.

Ethics declarations

Competing interests

One of the authors (S.R.F.) has an equity interest in Universal Display Corporation (UDC). This conflict of interest is under management by the University of Michigan’s Office of the Vice President for Research. The University of Michigan has a license agreement with UDC. The other authors declare no competing interests.

Peer review

Peer review information

Nature Photonics thanks Peter Bobbert, Martin Vacha and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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Extended data

Extended Data Fig. 1 Length scale of EL inhomogeneity.

(a) Example of Delaunay triangulation (white lines) between local EL intensity maxima in the inset area from Fig. 1b. A histogram of the segment lengths (Fig. 1e) provides one measure of the characteristic length of the EL inhomogeneity, \({d}_{{\rm{EL}}}=1.2\pm 0.2\) µm. (b) An alternative measure of the characteristic length is obtained from the radially-averaged autocorrelation function, which is computed by autocorrelating the image along all different directions and averaging the results. Radial autocorrelation is chosen because the two-dimensional fast Fourier transform is radially symmetric. The red line is a fit of the autocorrelation decay as a function of the radial image displacement, \(r\), using a Markovian model, \(A\left(r\right)=\exp (-2r/L)\)34, which yields a characteristic length of \(L\)=0.8 ± 0.2 μm.

Extended Data Fig. 2 EL inhomogeneity at different current densities.

Time-average EL images that correspond to the SOFI images acquired at different current densities of 4 mA-cm−2 (a) and 6 mA-cm−2 (b) in Fig. 2d,e, respectively.

Extended Data Fig. 3 EL inhomogeneity at different emission wavelengths.

Time-average EL images that correspond to the SOFI images acquired with 500 nm (a) and 600 nm (b) bandpass filters in Fig. 3b,c, respectively.

Supplementary information

Supplementary Information (download PDF )

Supplementary Notes 1–5 and Caption to Supplementary Video 1.

Peer Review File (download PDF )

Supplementary Video 1 (download MP4 )

Source video for Fig. 2a–c.

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Springsteen, J.D., Giebink, N.C. & Forrest, S.R. Nanoscale electroluminescence inhomogeneity and blinking in organic light-emitting diodes. Nat. Photon. (2026). https://doi.org/10.1038/s41566-026-01867-6

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