Organic materials have a huge potential as the main ingredient in cost-effective and clean energy technologies based on abundant and non-toxic materials. In particular, these compounds are being thoroughly investigated as the active layer in devices that convert light or waste heat into electricity, i.e. photovoltaic and thermoelectric technologies, respectively. Interestingly, no fundamental limitation has yet been discovered that says that organics cannot deliver devices with high efficiencies. Indeed, the library of potential candidates is literally infinite, as there is an infinite way in which carbon atoms can form conjugated systems through alternating single and double bonds. The issue is how to find such the best possible material for a given application. While theory points towards some directions, the final performance of the synthetized compounds strongly depends on specific properties of the materials made which, thus far, cannot be predicted. One of the major bottlenecks is the time needed to evaluate each compound. For instance, at lab scale, the fabrication of an organic solar cell takes from days to a few hours (if processed in parallel), while measuring its efficiency takes just minutes.
In order to identify very efficient organic energy systems in a time effective manner, the project FOREMAT proposed the use of high throughput screening methodologies based on samples with controlled gradients in the parameters of interest acting as processing libraries, combined with innovative imaging methods that enable the correlation between device performance and the information about the local parameters of the device.
The FOREMAT team has successfully introduced a series of methods to produce samples with 1D and 2D gradients in film thickness, composition, nanostructure, molecular orientation and doping level. We have also developed imaging methods to co-locally determine the device properties (e.g. photocurrent in solar cells, or thermal conductivity in thermoelectrics) and material´s properties. The resulting platform provides hundreds to thousands data points per system, making the evaluation of a novel system 50 times faster and saving up to 90% of the raw materials in the process. We have applied this technology to investigate tens of photovoltaic and thermoelectric systems, making significant advances both in terms of fundamental understanding and at applied level.
This technology addresses an important challenge for society, namely, the decarbonisation of the energy sources. In particular, the advanced technology will be used to efficiently identify materials and processes with very low carbon footprint, and simultaneously, finely adapted to the application. For instance, heat sources have all very different specifications in terms of operational temperatures and shapes, and therefore, the opportunity of choose thermoelectric materials with targeted performance is extremely relevant to maximize heat waste recovery, and thus energy efficiency. On the other hand, the widespread implementation of photovoltaics requires very different technologies depending on the application, for instance, very efficient cells for solar farms, semi-transparent and light weight for agrovoltaics, flexible for powering portable electronics, in-door lighting optimized for IoT applications, and colour tuneable and resilient to light incidence angle for façade decoration. FOREMAT´s technology will have a huge impact to society providing the means to advance photovoltaics a la càrte.
