1. Center for Photonics and Optoelectronic Materials (POEM), Department of Electrical Engineering and the Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544, USA
2. Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA

Correspondence to: S. R. Forrest¹ Correspondence and requests for materials should be addressed to S.R.F. (e-mail: Email: forrest@ee.princeton.edu).

Abstract

To obtain the maximum luminous efficiency from an organic material, it is necessary to harness both the spin-symmetric and anti-symmetric molecular excitations (bound electron–hole pairs, or excitons) that result from electrical pumping. This is possible if the material is phosphorescent, and high efficiencies have been observed in phosphorescent^{1, 2} organic light-emitting devices³. However, phosphorescence in organic molecules is rare at room temperature. The alternative radiative process of fluorescence is more common, but it is approximately 75% less efficient, due to the requirement of spin-symmetry conservation⁴. Here, we demonstrate that this deficiency can be overcome by using a phosphorescent sensitizer to excite a fluorescent dye. The mechanism for energetic coupling between phosphorescent and fluorescent molecular species is a long-range, non-radiative energy transfer: the internal efficiency of fluorescence can be as high as 100%. As an example, we use this approach to nearly quadruple the efficiency of a fluorescent red organic light-emitting device.

1. Center for Photonics and Optoelectronic Materials (POEM), Department of Electrical Engineering and the Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544, USA
2. Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA

Correspondence to: S. R. Forrest¹ Correspondence and requests for materials should be addressed to S.R.F. (e-mail: Email: forrest@ee.princeton.edu).