The discovery of electroluminescence in semiconducting polymers at Cambridge University¹ generated the most interest in semiconducting polymers since their discovery². Our paper³ describes two key advances. First, we demonstrated how to make a light-emitting diode using soluble semiconducting polymers, which lend themselves to easy coating processes on many different substrates. We selected a class of polymers, which are soluble in the semiconducting state, so that it is simple to deposit them onto even a plastic substrate that cannot withstand high temperature processing. Second, by varying the cathode material, we demonstrated light-emitting diodes that emit bright light at low voltages and high enough efficiency to permit their use in practical applications. Earlier polymer light-emitting diodes suffered from these two drawbacks.

The two advances described in the paper continue to generate a great deal of scientific and industrial excitement. The technology makes possible applications such as low-cost flexible light-emitting diodes and printed displays and continues to motivate scientific efforts to better understand semiconducting polymers and engineering efforts to improve semiconducting polymer devices.

Applied Physics Letters is a journal that publishes important and timely advances in applied physics relatively quickly and reaches the audience most likely to make use of such work.

  If you performed your research again, or published your paper again, what, if anything, would you do differently and why?

1. I would have made the dotted data points in figures 1 and 2 larger and darker. Some people, who only read photocopied or faxed versions of the article missed these data.
2. I would have reported the LED brightness in cd/m², rather than just the efficiency in photons/electron.
3. Many important advances have occurred since the paper was published. I didn’t think of them or carry them out at the time.

  What would you like to convey to the general public about your work?

In the future, semiconducting polymers will make possible exciting technology that we can imagine now as well as new developments that await discovery. Most semiconducting polymers derive from petrochemicals. If we burn those petrochemicals, we will miss out on the chance to use the materials in more important ways.

  What are the implications of your work for the future of your field or neighboring fields?

The neighboring fields that have benefited and will continue to benefit most directly are the areas of low-cost electronics and plastic solar cells. Printed integrated circuits, image sensors, polymer diode lasers, and solar cells based on semiconducting polymers make use of device fabrication and bandgap engineering techniques similar to those used in our work. The qualities of materials and our understanding of their chemistry, physics, and materials science improve each year!!

  How do you see the current state of affairs in your field and its prospects for the future?

1. J.H. Burroughes, D.D.C. Bradley, A.R. Brown, R.N. Marks, K. Mackay, R.H. Friend, P.L. Burns, and A.B. Holmes, "Light-emitting diodes based on conjugated polymers," Nature 347(6293): 539-41, 11 October 1990.
2. C. K. Chiang, C. R. Fincher, Jr., Y.W. Park, A. J. Heeger, H. Shirakawa, E. J. Louis, S. C. Gau and A. G. MacDiarmid, "Electrical Conductivity in Doped Polyacetylene," Phys. Rev. Lett. 39(17): 1098-101, 1977.
3. D. Braun and A.J. Heeger, "Visible Light Emission from Semiconducting Polymer Diodes," Appl. Phys. Lett. 58(18): 1982-4, 6 May 1991.