Next Generation Organic Semiconductor Lasers

This project will bring together materials, optics and laser expertise in St Andrews and Karlsruhe to make a new generation of organic semiconductors lasers. These lasers will use carbon-based semiconductors. The project will involve studying the photophysical and lasing properties of the new materials and then develop lightweight flexible lasers made from them.

The first laser used a crystal of ruby to amplify light. We aim to make lasers from much more readily available materials. In particular, we will work with organic semiconductors, which are remarkable plastic-like materials that combine the simple fabrication of plastics with the electrical and optical properties of semiconductors. When a voltage is applied to a thin layer of these materials they give out light, and the resulting device is called an organic light-emitting diode (OLED). Very recently we made a major breakthrough showing that an OLED can be integrated with a polymer laser to make an electrically driven laser.

The most recent generation of OLEDs emit by a process called thermally activated delayed fluorescence (TADF). The idea of the research project is to explore these and other organic semiconductors for use in lasers, thereby making a new class of laser. So far TADF materials have been developed and studied almost entirely for applications in OLEDs and displays.  The requirements for lasers are related (e.g. light emission is required) but not identical.   In particular all organic lasers tend to accumulate triplets which can then stop the laser action, leading to pulsed operation.  Sometimes this problem is managed by putting in a material to remove triplets, but that also wastes their energy.   In contrast we will explore TADF and other materials that can convert the undesired triplets into useful light emission providing a very interesting route to overcoming this problem. 

The project will start in St Andrews, and the first major task will be to study the gain and triplet dynamics of candidate laser materials.  This will involve measurements of transient absorption and transient luminescence.  Distributed feedback lasers will then be made from promising materials and their dynamics studied. Research in Karlsruhe will include developing a rate equation model of laser operation. It will also use the Karlsruhe Nano Micro Facility KNMF.  Furthermore, Karlsruhe Insititute of Technology (KIT) has an outstanding expertise in two-photon direct laser writing which not only gives a similar resolution to electron beam lithography but also enables 3D structures to be made.  

At the end of the project we aim not only to have demonstrated high performance lasers made from TADF and related materials, but to have identified the key materials design considerations for TADF lasing and a validated rate equation model of TADF lasing that many groups will find useful for the development of these new devices. The research student will gain valuable knowledge and skills relating to lasers, photophysics, materials and nanofabrication.

The project will be managed jointly between the School of Physics and Astronomy at St Andrews and the Karlsruhe Institute of Technology in Germany. The student will be supervised by Professor Ifor Samuel and Professor Graham Turnbull (University of St Andrews) and Professor Uli Lemmer (Karlsruhe Institute of Technology).

Informal enquiries regarding this scholarship may be addressed to Professor Ifor Samuel – email idws@st-andrews.ac.uk or Prof Graham Turnbull gat@st-andrews.ac.uk