Real-world applications of Moorfield products in science
Green Emissive Blends in OLETs
Paper Abstract
Organic light-emitting transistors are photonic devices combining the function of an electrical switch with the capability of generating light under appropriate bias conditions. Achieving high-performance light-emitting transistors requires high-mobility organic semiconductors, optimized device structures, and highly efficient emissive layers. In this work, we studied the optoelectronic response of green blends (TCTA:Ir(ppy)3) with varying doping concentrations in the limit of field-effect within a transistor device configuration. Increasing the dye concentration within the blend leads to a quenching of the photoluminescence signal; however, when implemented in a multilayer stack in a transistor, we observed an approximately 5-fold improvement in the light output for a 10% Ir(ppy)3 doping blend. We analyzed our results in terms of balanced charge transport in the emissive layer, which, in the limit of field-effect (horizontal component), leads to an improved exciton formation and decay process. While the performances of our devices are yet to achieve the state-of-the-art diode counterpart, this work demonstrates that engineering the emissive layer is a promising approach to enhance the light emission in field-effect devices. This opens the way for a broader exploitation of organic light-emitting transistors as alternative photonic devices in several fields, ranging from display technology to flexible and wearable electronics.
How Moorfield products helped:
Low temperature organic thermal evaporation
Devices were fabricated using our Moorfield Nanotechnology MiniLab90 equipped with four LTE (low temperature evaporation) sources for organic deposition and two TE (thermal sources) for metal evaporation. Film fabrication was carried in vacuum at a base pressure of 10–7 mbar. Amorphous Ir(ppy)3 thin-film (30 nm thick, at a rate of 0.15 Å/s) and TCTA:Ir(ppy)3 blends (60 nm) were deposited on a precleaned quartz substrate in vacuum at a base pressure of 5 × 10–7 mbar. The deposition rate for the host was kept constant (1 Å/s) for all blends.