Monolithic Integration of Oxide Transparent Multilayer Photonic Crystal as Optoelectronic Gate Dielectric into Organic Light-Emitting Transistor Platform

Organic light-emitting field-effect transistors (OLETs) are emerging opto-electronic devices that combine the capability of light generation with the switching properties of field-effect transistors [1]. Given the in-plane geometry and the lateral charge injection, OLETs possess a huge technological potential for the realization of bright and efficient nanoscale light sources [2]. Though, the full compatibility of OLET devices with well-established electronic and photonic planar technologies is still to be fully demonstrated by developing optical communication and integrated optoelectronic systems. At this porpoise, here we propose a strategy for tuning the optical and photonic features of single-layer ambipolar OLET in terms of emitted optical power, color coordinate and angular emission profiles by monolithically integrating a transparent oxide multilayer Photonic Crystals (PhCs) as optoelectronic gate (OEG) dielectric in the device planar architecture. The 1D PhC consists in an alternating stack of ZrO2/Al2O3 nanometric-thick layers which are deposited by Pulsed Laser Deposition onto glass/ITO substrate. This technique guarantees control over optical quality, high surface area packing density, wide substrate and platform compatibility. Moreover, the intrinsic planar 1D geometry of the multilayer PhC allows the organic active layer to preserve the morphological and structural features essential for efficient field-effect transport. The multistack is optimized in order to obtain the highest contrast in refractive indexes values together with high density and low superficial roughness in every single layer. A throughout simulation of the optical properties of multilayer PhC allows to engineer the number and thickness of the layers comprising the multistack for guaranteeing the coupling between the microcavity modes and the dipoles of the OLET active material [3]. Indeed, we implement a new-synthetized ambipolar electroluminescent thieno(bis)imide semiconductor as active material [4] in the bottom-gate top-electrode device configuration. The engineering of the integrated photonic device results in the enhancement of the overall optoelectronic performances, i.e. x6 and x10 factor in the emitted-power and brightness, and the achievement of non-lambertian light spatial distribution and modulation of the electroluminescence spectrum. Finally, the collected data allow us to consider the integration of photonic-active planar 1D PhCs as gate dielectric in OLETs a key element paving the way for further improvement in the realization of the long-searched-for electrically pumped organic laser. [1] Muccini, M. Nature Mat., 5, 605 - 613, 2006 [2] Capelli, R., et al. Nature Mat., 9, 496-503, 2010 [3] Frezza, L., et al. J. Phys. Chem. C, 115 (40), 19939-19946, 2011 [4] Melucci M., et al. Chem. Comm. 47, 11840-11842, 2011