Hybrid Organic Semiconductor Gallium Nitride CMOS smart pixel arrays

Project: Standard

Project Details

Key findings

The project successfully realised its initial vision of micro-systems integrating three largely disparate technologies: micro-scale light-emitting diodes (LEDs) based on the inorganic semiconductor gallium nitride (GaN), custom silicon-based control circuitry using established CMOS principles, and light-emitting elements based on organic and other 'soft' luminescent materials. Several objectives concerned optically pumped lasing (OPL) in organics, and major advances were made in understanding the conditions needed to achieve pulsed lasing reproducibly and with low thresholds. We successfully achieved OPL with custom designed GaN micro-LEDs, building on our results achieved with commercial broad-area LED pumping from the start of the project. Concerning integrated micro-systems combining all three of the core technologies, a well-publicised example from joint work between the St Andrews, Edinburgh and Strathclyde groups is a compact microsystem detector for explosives, which takes advantage of the interactions between a light-emitting polymer and the vapours given off by common high explosives. We also demonstrated the application of an LED-pumped organic laser as a sensor for nitroaromatic explosive molecules. The work on compact sensors for explosives was featured in an article in Chemistry World magazine, and interviews on the BBC Naked Scientists radio programme and an American Institute of Physics podcast.

The project also produced major advances in each of the three discrete technology areas. The design and implementation of silicon CMOS circuits and GaN micro-LED sources were the responsibilities of the Edinburgh and Strathclyde Institute of Photonics partners, but the design iterations involved close interactions with St Andrews to address the very challenging requirements for OPL in organics. A notable and very significant advance made with the GaN micro-LEDs involve the scope for fast modulation of the emitted light, such that these sources, either through direct emission or in conjunction with an organic colour converter, can transmit data-streams at useful rates for visible light communications (VLC). Proof-of-concept demonstrations made during HYPIX underpinned major follow-on funding in VLC involving the partners from Strathclyde, St Andrews and Edinburgh.

There were a number of important advances in the development of organic semiconductor lasers, a key objective of the collaborative work in St Andrews. The project consortium greatly benefited from the custom synthesis of organic semiconductors by the team from Strathclyde Chemistry, who provided several families of new materials through the project. Detailed photo-physical characterisation of novel materials, and assessment of their potential as lasing media, was performed in St Andrews, and also by the Imperial College group. Ultrafast photophysics studies in St Andrews, in collaboration with the Strathclyde chemistry group and also theorists at Heriot-Watt University, has led to new insight to the fundamental photonic processes in star-shaped organic molecules, and to the molecular design of optimised organic laser gain media. Particularly notable progress was made in the application of nanoimprint lithography for patterning organic materials with resonator nanostructures necessary for OPL. Advances made in St Andrews have achieved a 100-fold reduction in OPL threshold density, compared with the published state-of-the-art for organic lasers fabricated by UV nanoimprint.

Finally, the project featured an Open Day, and numerous exchange visits in which PhD students and postdoctoral researchers made extended working visits to partner laboratories. This latter aspect was singled out for consistent praise by the project mentor, and has trained a group of early-career researchers in effective cross-disciplinary collaboration.
AcronymHybrid organic semiconductor/ gallium
Effective start/end date1/10/0830/09/12


  • EPSRC: £853,569.10


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