Tailoring interfaces in Earth abundant thin film solar cells

Cu2ZnSn(S,Se)4 (CZTSSe) is a promising photovoltaic material with outstanding optoelectronic
properties and Earth abundant constituents. Among the variety of techniques employed for the
preparation of the absorber layer, solution-based deposition and processing has the potential to
provide low-cost scalable routes to produce photovoltaic devices with high efficiency. Such
results include the current record efficiency for CZTSSe solar cells at 12.6 % using hydrazinesolution
based method. On the other hand, nanoparticle inks offer an alternative to avoid using
the highly toxic and potentially explosive solvent, hydrazine. Deposited from the Cu2ZnSnS4
(CZTS) nanoparticle inks, the CZTS precursor thin films annealed in the presence of Se can
provide devices with efficiency up to 9.5%.
Northumbria has recently developed a route for fabricating and controlling the electronic and
structural properties of nanoparticle inks. Upon heat treatment a dense and compact film is
formed that can be used to fabricate solar cells with efficiencies approaching 7% on rigid
substrate or a bit less if we use flexible foils. Our attention now focuses on the interfaces within
the solar cell structure and particularly the pn junction.
The key aim of this project is to develop single/multilayer n-type buffer layers using
indium/cadmium/zinc sulphide and zinc/titanium oxide to increase device performance for both
rigid and flexible structures. During the study you will be in control of the complete fabrication
processes (nanoparticle inks, thin film and solar cells) and will have access to a wide range of
characterisation techniques and recently refurbished laboratories. You will also work closely with
one of our partners, TescanUK, to observe the layers nano/microstructure and chemical
composition while performing in-situ microscopy-stress tests (for example bending of flexible
films, heat treatment of the pn junction). This project is suitable for a candidate with strong
interest in semiconductor and device fabrication as well as spectroscopy and microscopy.

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.