Hybrid perovskite solar cell generates power from sun and rain

<p class="p1"><span class="s1">Researchers at ICMS in Seville have developed a hybrid perovskite solar cell that generates electricity from both sunlight and raindrops, using the photovoltaic and triboelectric effects. A fluorinated CFₓ polymer layer enables water resistance, triboelectric energy harvesting, and high light transparency without reducing solar cell efficiency.</span></p><p>Researchers at the Institute of Materials Science and Technology (ICMS) in Seville, Spain, have developed a hybrid cell that simultaneously converts solar radiation and raindrop impacts into electricity. While the perovskite component relies on the photovoltaic effect, the raindrop-to-electricity conversion uses the triboelectric effect.</p>
<p>The triboelectric effect occurs when two different materials come into contact and then separate, generating an electrical charge. Electrons transfer between the materials during contact, leaving a charge difference when they separate, which produces an electrical voltage. For instance, when a water droplet strikes a suitable polymer surface, the contact and subsequent flow or detachment create a charge separation that can be harvested as an electrical pulse via electrodes.</p>
<p>The team’s key innovation is a fluorinated polymer layer, known as a “CFₓ layer,” which performs multiple functions. It encapsulates and protects the perovskite layer from moisture, increases surface hydrophobicity to reduce water interaction, and exhibits triboelectric properties. Importantly, it maintains a high optical transparency of over 90% ensuring that photovoltaic performance is not compromised.</p>
<p>The CFₓ layer is deposited at room temperature under vacuum using plasma technology. According to the researchers, the coating leaves solar cell performance virtually unchanged, with the best cells achieving an efficiency of 17.9%.</p>
<p>For triboelectric energy generation, the chemical composition of the CFₓ layer was optimized. In one variant, the raindrop-driven generator reached open-circuit voltages of up to 110 V and a maximum power density of about four mW/m2.</p>
<p>The coating does not affect solar cell performance. In a hybrid setup combining photovoltaic and triboelectric generation, the system achieved a short-circuit current density of 11.6 mA/m2 at 0.5 suns of illumination. Voltage peaks of up to 12 V per impacting droplet were also measured.</p>
<p>In a demonstrator, the hybrid perovskite solar cell was used to charge a supercapacitor, with a specially developed boost converter enabling the continuous operation of a red LED strip. The authors note that the charging speed is primarily determined by the solar cell, while the triboelectric generator provides a supplementary contribution. Whether this concept can be scaled beyond laboratory prototypes remains uncertain.</p>
<p>This work is part of the 3DScavengers project, funded by the European Research Council (ERC Starting Grant), and the Drop Ener project, co-financed by the Next Generation Fund.</p>
<p>The researchers published their findings in <em>“</em><a href="https://www.sciencedirect.com/science/article/pii/S2211285525010377#fig0040" rel="noopener" target="_blank">Water-resistant hybrid perovskite solar cell – drop triboelectric energy harvester</a>,&#8221; published in <em>Nano Energy</em>.</p>