ITMO: Silicon Nanoantennas Make Solar Cells More Efficient

Solar panels are the driving force of wireless autonomous electronics. At their core are solar cells – electronic devices that convert light directly into electricity. The main obstacle to the widespread use of solar panels is their low efficiency: the maximum efficiency of solar panels at top laboratories reaches values of just about 26%. However, even the 26% figure is hard to obtain, as physicists have to comply with strict requirements such as sterile rooms and materials.

Solar cells and batteries in general can be improved by developing semiconductor materials that efficiently absorb light. Perovskites are considered promising since they are light, thin, and easy-to-produce and can be used to make thin solar cells with varied bending shapes, low weight, and multiple applications. Like other semiconductors, perovskites, however, absorb just a fraction of the spectrum and therefore generate less energy than they receive from the source.

To that end, ITMO scientists have developed perovskite solar cells using silicon-based optical resonant nanoantennas. Depending on their size and refractive index, nanoantennas resonantly scatter light, thus increasing its concentration in the perovskite at certain wavelengths (in this case, 500-800 nm). The method is suitable for different types of perovskite-based semiconductors that absorb light in various spectral ranges.

In an experiment, the physicists infused several nanoparticle solutions into a solar cell to magnify light in various wavelengths: blue, green, yellow, red, and near IR. The specialists tested the obtained samples via a sun simulator and measured the conversion rate.

The experiment showed that the efficiency of the cells increased as compared to the initial samples, which demonstrated a 19% rate. The best effect was achieved in two solutions of nanoantenna particles. The sample with nanoparticles with an average size of 160 nm showed a maximum efficiency of up to 20.5%; the efficiency of a sample with 140 nm nanoparticles, which scatter light in the green wavelength range, increased to 20.3%. The researchers are satisfied with the results of the study, as it was achieved in genuine systems, rather than in an ideal laboratory environment, which means the method can be massively introduced for a broader class of perovskite solar cells.

“We’re going to further improve our solar cells and broaden the range of their uses; in particular, we want to adapt them for diffuse sources (such as indoor lighting solutions), which come with their own spectral properties. We’ll also continue our work with nanoantennas. Perhaps, in the future, our solar cells will be used underwater or even in space,” says Aleksandra Furasova, the first author of the paper and a researcher at the Laboratory of Hybrid Nanophotonics and Optoelectronics of ITMO’s Faculty of Physics.