Dr. Kettle’s has been based in the School of Electronics at Bangor University since 2011. During this time, he has acquired over £1m of grant funding through Royal Society, Royal Academy of Engineering, Interreg, A4B, Ser Cymru and EC projects. He is co-I with the CLARET (Centre for Lifetime and Reliability Testing) which has worked with over 40 companies identifying failures in products and developing lifetime test protocols (http://claret.bangor.ac.uk). His expertise lies in semiconductor device fabrication, characterization and modelling. He completed a PhD in nano photonics and electronics in 2008, which was a joint collaboration between Swansea and Cardiff Universities. He has experience working in industry with two spin-out companies and a large multinational (Alcatel SEL). From 2010, Dr. Kettle was also employed with the Knowledge Centre for Material Chemistry (KCMC) £20m project in the north-west of England aimed at developing links between academia and industry. His current research projects are in sensor development, nanofabrication, solar energy, coating technologies and light emitting diodes and has published over 30 times in international journals.
Accelerated testing for predictive ageing in organic solar cells for outdoor applications
Accelerated Life Testing (ALT) is normally used to provide information on 1) a products failure mechanisms and/or 2) expected life in the field. Generally, ALT data analysis is separated into two distinct forms. Firstly, qualitative tests are used to compare the relative stability of products or to meet specific standards. Quantitative accelerated life tests are used for predictive ageing and tries to quantify this through the application of mathematical models. Currently, most ALT of organic photovoltaics (OPVs) in the literature is based on ‘ISOS consensus standards,’ which were devised by the OPV academic community to enable consistency when reporting lifetimes in literature. These are qualitative tests that are normally performed on small samples with the specimens subjected to a single severe level of stress, or multiple stresses (max. of 2), and limited to only one type of time-varying stress.
In this presentation, I will try to show how standard life test models can be applied to OPV modules to relate degradation in an indoor test chamber to data obtained outdoors from testing facilities at Bangor University. The degradation related to temperature, humidity, irradiance and thermal change has been studied. The results indicate that consensus test protocols (i.e. ISOS standards) do not provide a good enough range of stress conditions to accurately fit life test models to and therefore, additional testing data is needed. Multiple stress testing (i.e. light with additional factors such as temperature and humidity) is also required as OPV degradation is often related to the interaction between environmental stress factors.
Whilst the focus of this presentation will be on OPVs, many of the principles discussed are relevant to other plastic electronic products such as displays and sensors etc.