This proposal seeks to establish a unified framework for understanding the - theoretical and practical - limits to efficiency of molecular or nanostructured heterojunction solar cells. The approach is to quantify and optimize the amount of electrical work available per absorbed photon using luminescence based techniques, electrical measurements and modelling. As examples of technologically relevant material systems we will study polymer:fullerene, polymer:nanoparticle and dye sensitized oxide structures, with the aim of describing these different heterojunctions within a single framework. Our approach is to control the energy of the charge separated state at the heterojunction through variations in materials and processes used, detect and measure the energy of that state and compare with the absorbed photon energy and the free enrgy delivered to an external circuit. Particular questions to be addressed concern the effect of the dielectric permittivity of the heterojunction medium (by comparing all organic with hybrid heterojunctions); the effect of microstructure; and the difference in the requirements upon binary and ternary heterojunctions to enable charge separation. A second aim is to improve understanding of luminescence based characterization techniques and find new applications of the techniques. In the context of dispeersed heterojunctions such as polymer:fullerene solar cells, luminescence allows us to study the effect of different recombination mechanisms and compare in particular recombination at the internal polymer:fullerene interface with recombination at the electrodes. This could prove to be a valuable diagnostic method for a range of optoelectronic devices. For example, luminescence applied in-situ to photovoltaic device sduring manufacture can serve as a diagostic tool to indicate the sources of energy loss within the device. We have engaged an indutrial project partner to explore this application.

This project is centred on the development of the materials, device structures, materials processing and PV-panel engineering of excitonic solar cells (ESCs). These have the potential to greatly reduce both materials and also manufacturing costs where the materials, such as organic semiconductors, dyes and metal oxides, can be processed onto low-cost flexible substrates at ambient temperature through direct printing techniques. A major cost reduction is expected to lie in much-reduced capital investment in large scale manufacturing plant in comparison with conventional high vacuum, high temperatures semiconductor processing. There are extensive research programs in the UK and India developing these devices with the objective of the increase in PV efficiency through improved understanding of the fundamental processes occurring in these optoelectronic composites. However, there has been less activity in the UK and India on establishing from this science base a scalable, commercially viable processing protocol for excitonic solar cells. The scope of this UK-India call enables research and development to be undertaken which can pull together the set of activities to enable manufacturing application, and this extends beyond the usual scope of funding schemes accessible to the investigators. This project tackles the challenge to create cost-effective excitonic solar cells through three components: new material synthesis of lower cost materials; processing and development of device (nano)architectures compatible with low process costs; and the scale up towards prototypes which can replicate solar cell performance achieved in the research phase. The team includes leading scientists in the UK and India working on excitonic solar cells. Skills range from material synthesis and processing, device fabrication and modelling, wet processing of large area thin films, and PV panel manufacture and testing. Careful consideration has been made to match and complement the skills on both sides of the UK-India network. Further to this, engagement with industrial partners in both the UK and India will allow access to new materials, substrates etc., and access to trials and testing of demonstration PV panels in the field.

This project is centred on the development of the materials, device structures, materials processing and PV-panel engineering of excitonic solar cells (ESCs). These have the potential to greatly reduce both materials and also manufacturing costs where the materials, such as organic semiconductors, dyes and metal oxides, can be processed onto low-cost flexible substrates at ambient temperature through direct printing techniques. A major cost reduction is expected to lie in much-reduced capital investment in large scale manufacturing plant in comparison with conventional high vacuum, high temperatures semiconductor processing. There are extensive research programs in the UK and India developing these devices with the objective of the increase in PV efficiency through improved understanding of the fundamental processes occurring in these optoelectronic composites. However, there has been less activity in the UK and India on establishing from this science base a scalable, commercially viable processing protocol for excitonic solar cells. The scope of this UK-India call enables research and development to be undertaken which can pull together the set of activities to enable manufacturing application, and this extends beyond the usual scope of funding schemes accessible to the investigators. This project tackles the challenge to create cost-effective excitonic solar cells through three components: new material synthesis of lower cost materials; processing and development of device (nano)architectures compatible with low process costs; and the scale up towards prototypes which can replicate solar cell performance achieved in the research phase. The team includes leading scientists in the UK and India working on excitonic solar cells. Skills range from material synthesis and processing, device fabrication and modelling, wet processing of large area thin films, and PV panel manufacture and testing. Careful consideration has been made to match and complement the skills on both sides of the UK-India network. Further to this, engagement with industrial partners in both the UK and India will allow access to new materials, substrates etc., and access to trials and testing of demonstration PV panels in the field.

UK and India are both rising stars in the promotion of Solar Energy viz. direct generation of electricity from the Sun called photovoltaics (PV). In the UK, PV is seen as a key technology to reduce the carbon footprint of electricity generation. It is also a necessity if future building standards are to be met, which will require on-site generation. PV is the only way to meet this to date. DECC has announced recently 'The Solar Strategy' which promotes the deployment of solar technologies on the existing buildings. In India PV has the added benefit that it is a highly scalable technology that can be deployed to support the grid infrastructure and indeed can be built possibly faster than conventional power plants through terrestrial solar farms and BIPV sectors. The current APEX program stems from the strategic move by the governments of the UK and India who jointly identified Solar Energy as an area of significance in providing solutions to the problem of meeting future energy needs. This partnership was aimed at linking the strengths of both countries to enhance the research capabilities of both nations. APEX had been focusing on the development of new functional materials, device structures, materials processing and engineering of photovoltaic modules utilising excitonic solar cells (ESCs). These are a class of nano-structured solar cells based on organic nano-composites and dye-sensitised nanocrystalline TiO2 materials. The current state-of-the-art power conversion efficiency (PCE) figures ~11.4% and ~9.2% has been achieved in liquid junction dye sensitized solar cell (DSSC) and organic solar cells (OSC), respectively. In the pursuit of achieving high efficiency solid state DSSC, a new breakthrough has been established recently through our Oxford group (Prof. Henry Snaith) who achieved >17% efficient solid state devices using pervoskite solar cells. Thus, the APEX team enjoys the exceptional, world-class capability in Excitonic PV technology. The success of the program had been through its novelty, innovation and cutting edge R&D capability it possesses.