PolyU Develops Organic Solar Panels with Increased Efficiency and Longer Life

Many see solar energy as a solution for the future, despite the fact that it brings many problems. In particular, it is an uneven supply of energy throughout the day and year. With ever-improving energy storage technologies, this may gradually decrease, however 100% solar generation would certainly not be feasible worldwide (it is pretty well covered by wind farms, though). The development of new solar cells tries many different paths, either by further improving the silicon ones or by finding completely new materials that could convert solar energy into electricity. One such path is i organic solar panels (OSC). Scientists at the Hong Kong Polytechnic University (PolyU), for example, are working on them. In their case, they used 1,3,5-trichlorobenzene (TCB) to improve the properties of already existing cells. The result is higher efficiency and longer life.

E.g. cells using PM1:BTP-eC9 technology using diiodooctane (DIO) achieved an efficiency of 17.86%, while the new process with TCB increased it to 19.10%. In the case of systems with PM6:BTP-eC9, the efficiency increased from 17.98% with DIO to 19.31% with TCB. Although it is only 1.3 percentage points, it also means an additional 7% increase in efficiency (resulting in 7% more electricity than before). The certified efficiency of the new cells is slightly lower and amounts to 18.93%.

However, the lifetime of organic solar cells is still something that needs to be worked on. If we focus on the more efficient variant PM6:BTP-eC9, the version with DIO lost 17% of the maximum efficiency in the first 75 hours, which is a really significant difference. The TCB variant fared significantly better, but even a 7% loss of efficiency is not completely low. The T80 (pair at 80% of the maximum) for the novelty came after 660 hours of illumination corresponding to sunlight (in our conditions, this corresponds to about 4 months). However, as can be seen on the graph, the efficiency then stabilizes quite a bit and after 1000 hours it dropped to 78% for the new version (that is, only after another 340 hours from reaching T80). The DIO variant after 1000 hours was at 69%. But in order for such panels to make at least some sense, the service life would have to be increased by at least an order of magnitude.