THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:
Optical spectroscopy: from a luminescent molecule to working OLED devices
MSc Larissa Gomes França
Department of Physics , Durham University – UK
Organic light-emitting diodes (OLEDs) have attracted tremendous interest from the luminescent display industry over the last years. Nowadays, this technology is already a part of peoples’ lives as being used in everyday items such as in mobile phones and televisions. Using organic semiconductors instead of the more traditional inorganic (i.e. GaN, InGaN, GaAs, etc.) introduces many technological advantages. Among them are flexibility, very low thickness of final luminescent displays as well as possibility to produce transparent displays and luminaries. In an OLED device, applied voltage bias induces injection of electrons and holes through the device cathode and anode, respectively. The charge carriers are transported through the device and migrate to the emissive layer where they recombine, generating light. Spin statistics based on the spin states of holes and electrons undergoing recombination leads to a 1:3 ratio between multiplicities of thus produced excited states: singlets and triplets. Considering that often triplet states do not contribute to the luminescent output of an OLED the efficiency of these devices becomes limited to 25% of what it could be. Mechanisms that enable turning non-emissive triplet states into luminescent singlets will be discussed in this talk. Key parameters to maximise efficiency of these mechanisms allowing 100% utilisation of all electron-hole recombination will also be covered.
Date: November 4, 2022 – (friday) – Time: 10:15 a.m.
Local: Auditório do Departamento de Física