With up to 20% of electrical energy being consumed by lighting, it is important to use this energy wisely. Replacing the inefficient light generation technologies of today with solid state lighting based on gallium nitride (GaN) light emitting diodes (LEDs) will enable us to reduce this 20% to 10% or even 5%. However, several factors need to be addressed to accelerate the uptake of this emerging technology. These are obtaining an acceptable and controllable colour from the lighting units while reducing the capital cost through large scale process technologies. This project proposes the development of AlGaInN materials and structures to achieve much higher efficiencies at blue-green and yellow light wavelengths enabling highly luminous and controllable light generation. The approach in this proposal is based on reducing the internal electric fields in the light emitting quantum well material through the development of semi-polar GaN templates on large area sapphire and silicon substrates. The growth process development and optimisation will be informed by modelling of the surface reactions and through timely and detailed characterisation of the material properties. Growth of quantum dots within a quantum well in a low electric field environment will allow internal quantum efficiencies to reach >70% in the blue and >35% in the yellow spectral regions. The material quality will be verified in demonstration LEDs which will be benchmarked against current devices. Issues around the scaling of the technology to a manufacturing environment and 100 mm diameter substrates will be addressed. This approach can lead ultimately to efficacies of over 200 lumens/W with colour rendering indices >90%. European science will benefit through the new knowledge, while European industry can be more competitive by adopting the new processes and the European citizens will benefit from a higher quality of light in their everyday environment and reduce drastically the costs for lighting.