Developing Truly Green Solar Cells

The global community is currently facing some of the biggest issues of the past century, one in particular is the amount of waste we are producing. Due to the single use consumer lifestyle, there has been an uncontrolled amount of waste produced, which has not been disposed of in a sustainable manner. There are a number of value materials discarded, such a precious metals present in phones, computers and batteries. To aid a circular economy, this project will aim to try and reuse some of this waste to develop a solar cell, whilst also combats some of the environmental issues surrounding the next generation of solar energy. The first generation solar cells were based around silicon, historically these cells were expensive to produce and required high amounts of energy. This gave rise to research into the next generation of solar cells, which maintains the same efficiencies but at a lower cost both financially and in energy, however these cells have some environmental issues. These issues are mainly focused around the materials used in the absorber material. One problem is the use of highly toxic materials such as lead in perovskite solar cells and the use of rare elements which includes indium and gallium used in the Copper Indium Gallium Selendie (CIGS) solar cells. The materials for this project must be non-toxic and earth abundant with specific criteria based on their bandgap, ability to absorb light and stability of the excited state. Some material which will be of interest include antimony, copper, tin and iron. To ensure the circular economy aim of this project is met, it will focus on trying to extract materials for the absorber materials from a recycled source. The sources of interest for these materials include industrial waste water, soil surrounding mines and electrical equipment due to the high quantities of materials present. This project aims to adopt these materials into a thin film solid state device which has a similar structure to a Dye Sensitized Solar Cell (DSSC), however with an extremely thin absorber layer (ETA) instead of a dye material. When fabricating these devices, the ETA thickness will be of paramount importance, it must be extremely thin to avoid any disruption to the diffusion pathway of the charge carriers. Initially, the solar cell will have a planar structure and another orientation is a bulk heterojunction. This orientation aims to maximise the surface area of the absorber material which should increase the charge carriers and in turn increase efficiency. The films will be deposited through a range of well-known techniques such as spin coating, chemical bath deposition and silar. These devices will be optimised through the various deposition techniques, different thicknesses and compatible materials for the other parts of the cell. Once made, the devices will be characterised to gain as much information as possible. To characterise the devices, a Scanning Electron Microscope (SEM) will be employed to see the layers of the solar cell which allows thickness measurements, defect detection and intermixing of layers. Alongside this, High Resolution Transmission Electron microscope (HRTEM) will be used to further investigate areas highlighted by SEM measurements. This gives the ability to focus on the atomic scale of the material due to the high resolutions. X-ray Diffraction (XRD) will be used to understand the crystalline structure of this layer. To electrically characterise the performance of the devices a solar simulator will be used. This technique will expose a selected area of the devices to the equivalent of one sun. This allows the production of current voltage curves, from this the extraction of the voltage open circuit, the current short circuit and overall efficiency can be found. To gain a further understanding of the charge carrier lifetimes in the absorber layer, scanning tunnelling spectroscopy will be used.

ReNU's enhanced doctoral training programme delivered by three uniquely co-located major UK universities, Northumbria (UNN), Durham (DU) and Newcastle (NU), addresses clear skills needs in small-to-medium scale renewable energy (RE) and sustainable distributed energy (DE). It was co-designed by a range of companies and is supported by a balanced portfolio of 27 industrial partners (e.g. Airbus, Siemens and Shell) of which 12 are small or medium size enterprises (SMEs) (e.g. Enocell, Equiwatt and Power Roll). A further 9 partners include Government, not-for-profit and key network organisations. Together these provide a powerful, direct and integrated pathway to a range of impacts that span whole energy systems.

Industrial partners will interact with ReNU in three main ways: (1) through the Strategic Advisory Board; (2) by providing external input to individual doctoral candidate's projects; and (3) by setting Industrial Challenge Mini-Projects. These interactions will directly benefit companies by enabling them to focus ReNU's training programme on particular needs, allowing transfer of best practice in training and state-of-the-art techniques, solution approaches to R&D challenges and generation of intellectual property. Access to ReNU for new industrial partners that may wish to benefit from ReNU is enabled by the involvement of key networks and organisations such as the North East Automotive Alliance, the Engineering Employer Federation, and Knowledge Transfer Network (Energy).

In addition to industrial partners, ReNU includes Government organisations and not for-profit-organisations. These partners provide pathways to create impact via policy and public engagement. Similarly, significant academic impact will be achieved through collaborations with project partners in Singapore, Canada and China. This impact will result in research excellence disseminated through prestigious academic journals and international conferences to the benefit of the global community working on advanced energy materials.