Organic materials have huge potential as the main ingredient in cost-effective and low energy payback time clean energy technologies based on abundant and non-toxic material systems. In particular, these materials are being thoroughly investigated as the active layer in devices that convert light or waste heat into electricity, i.e. photovoltaic and thermoelectric technologies.
Interestingly, no fundamental limits have been discovered suggesting that organic photovoltaic and thermoelectric materials with extremely high efficiency cannot be synthetized. 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 amazing materials. While theory points towards specific directions, the performance of the synthetized compounds strongly depends on specific properties such as molecular weight, sidechains, solubility or packing tendency, thus one should be talking about material families.
One of the major bottlenecks is the time needed to evaluate each compound, let alone a full system family. For instance, at lab scale, the fabrication of an organic solar cells takes between 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, ICMAB researchers, led by Dr. Mariano Campoy-Quiles, have developed a combinatorial platform which includes advanced processing and imaging to make 50 times faster the photovoltaic evaluation and optimization of a system. The study is published in the Advanced Electronic Materials journal.
They have combined several solution processing methods in order to produce films exhibiting 2D gradients in the parameters of interest, which are equivalent to more than 100 conventional samples. Then, these samples were analyzed using photocurrent and Raman imaging in order to correlate one to one the device performance and structural information (thickness, composition, nanostructure). In order to verify the strength of the developed technology, they optimize three different systems, namely P3HT:ICBA, PCDTBT:PC70BM and PffBT4T-2OD:PC70BM, obtaining efficiencies approaching 4 %, 6 % and 10 %, respectively, using less than 100 mg of each polymer in the process.
The study was financed by the Ministerio de Economía y Competitividad of Spain through the “Severo Ochoa” Programme for Centres of Excellence in R&D and by the European Research Council (ERC) project "Finding a needle in a haystack: efficient identification of high performing organic energy materials (FOREMAT)".
High‐Throughput Multiparametric Screening of Solution Processed Bulk Heterojunction Solar Cells. Antonio Sánchez‐Díaz Xabier Rodríguez‐Martínez Laura Córcoles‐Guija Germán Mora‐Martín Mariano Campoy‐Quiles. Advanced Electronic Materials. First published: 12 February 2018. https://doi.org/10.1002/aelm.201700477