Researchers in Mexico have enhanced optoelectronic and solar cell performance by combining melanin with porous silicon powder. The compound improved photocurrent generation by boosting the luminescence of the silicon material.
A group of researchers led by Mexico’s National Institute of Astrophysics, Optics and Electronics (INAOE) has developed a new colloidal solution that could reportedly increase the efficiency of optoelectronics devices and solar cells.
“The solution integrates melanin and porous silicon (PSi) powder, a combination that was previously studied for use in heterojunction solar cells,” the research’s corresponding author, Alfredo Benítez Lara, told pv magazine. “As melanin consists of indole derivatives having positive and negatively charged groups, it can in principle form complexes of various types acting as an electron acceptor and/or an electron donor.”
The team sought to increase the compound’s photocurrent generation capability by increasing PSi luminescence through the addition of melanin in different amounts on PSi films. It initially formed a PSi substrate via the electrochemical etching process of a p-type silicon wafer. This process was executed in a 3D-printed reactor, with melanin being dissolved with dimethyl sulfoxide (DMSO) by mechanical stirring.
The scientists used melanin provided by Mexican specialist Evogenia to create a heterojunction through the drop-casting technique, which is simple film-forming technique adopted by many research groups as it does not imply the utilization of specific equipment. They deposited the melanin onto the PSi film at a temperature of 90 C.
“The melanin contributes with the increment of luminescent recombination centers through bondings with silicon and the aromatic rings,” they explained. “In other words, bonds between silicon and the elements from the melanin such as carbon, oxygen, and hydrogen are created.”
The group observed an increment in luminescence in the range of 500–700 nm, which was described as correlated to luminescent defects. Infrared (FT-IR) and photoluminescence (PL) confirmed that the melanin-functionalized samples displayed an increment of the peaks at 790 nm, 878 nm, 943 nm, and 1,043 nm.
“The melanin redox properties are enough to passivate the PSi, creating luminescent recombination centers whit a shift and increment in the PL response,” the researchers stressed, noting that the carrier lifetime reduces in each sample with the increment of melanin. “This heterojunction could be applied to build optoelectronic devices with fast response in the UV region,” they concluded.
They presented their findings in “Synergistic effects of vegetal melanin and porous silicon powder to improve the efficiency of solar panel,” published in Solar Energy.
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