Features of light to current transformations in organic devices

Abstract

Organic semiconductors generate a tremendous interest in the development of light weight and flexible electronic devices owing to their ease of fabrication and suitability to large area applications. However, there are many possibilities left unexplored for these conjugated materials. We discuss here a new structure that permits efficient integration of both light and current generation functions from a rubrene/fullerene heterostructure into an efficient Organic Dual Device (ODD)6'7. The solar power conversion efficiency reaches 3 % with 5.3 mA/cm2 short-circuit current density and almost 1 V open circuit voltage under AM 1.5 illumination. Surprisingly, the EL turn-on voltage is below IV, about half of the rubrene band gap (2.2 eV), that cannot be explained using current models of charge injection into organic semiconductors. A physical interpretation is proposed in terms of the so-called Auger fountain mechanism that we could implement into our molecular heterojunction.