Researchers at Mexico’s National Institute of Astrophysics, Optics and Electronics (INAOE) have managed to improve the performance of solar cells and optoelectronic devices by combining natural melanin pigment with porous silicon powder. The compound enhanced photocurrent generation by boosting the luminescence of silicon, in other words, its ability to emit light. The study findings were published in Solar Energy Journal.
The Mexican scientists have developed a colloidal solution using melanin and porous silicon. The combination has previously been considered as a promising option for use in heterojunction solar cells. Melanin contains positively and negatively charged groups and can act both as an electron donor and acceptor thus participating in charge transfer.
For their experiment, the scientists created a porous silicon substrate using the electrochemical etching method of a p-type silicon wafer in a 3D-printed reactor. They then dissolved melanin with dimethyl sulfoxide (DMSO) and applied it to the silicon film using the drop-casting method, a simple coating technique that does not require specialized equipment. The process was executed at a temperature of 90 °C. The chemical interaction between silicon atoms and melanin elements (carbon, oxygen and hydrogen) resulted in the enhanced luminescence of the silicon material. This led to a greater number of areas where luminescence occurred, which, in turn, helped improve the material’s optical properties.
As a result of the experiment, an increment in luminescence in the range of 500-700 nm was recorded in the porous silicon emission spectrum, which was attributed by the researchers to specific defects appearing in the material. Further measurements revealed the emergence of new peaks in the infrared region at 790, 878, 943 and 1043 nm wavelengths. The scientists explain that melanin’s redox properties help stabilize the structure of porous silicon and facilitate the formation of effective recombination centers that enhance the material’s light-emitting characteristics.
It was further established that the carrier lifetime reduced with the increment of melanin content. It means that the material responds faster to external light effects, which can be especially useful in creating optoelectronic devices, such as sensitive sensors or photodetectors, with fast response in UV region.
