Researchers have developed a new solar cell, described as an "artificial leaf", which mimics the electron transfer of photosynthesis, at a much faster rate than observed in nature.
According to the study by researchers at Ruhr-University Bochum, the new method efficiently integrates photosynthetic proteins in photovoltaics, offering offers a new immobilization strategy that yields electron transfer rates exceeding for the first time rates observed in natural photosynthesis, which could open the possibility for the construction of semi-artificial leaves functioning as photovoltaic devices with drastically increased performance.
In leaves, photosystem 1 (PS1) absorbs light and its energy is finally utilized for the conversion of carbon dioxide to biomass, while photovoltaic devices, mostly build from silicon based semiconductors, also harness solar light but produce electricity.
The research team isolated a highly stable PS1 from thermophilic cyanobacteria that live in a hot spring in Japan. However, the integration of this natural component into artificial devices faces one major challenge. PS1 displays both hydrophilic and hydrophobic domains which complicate its immobilization on electrodes.
The scientists embedded PS1 in this artificial matrix and where able to fine tune the local environment of the natural photosynthetic proteins. The hydrophobic/hydrophilic properties of the hydrogel can be controlled by pH shift and were adjusted to the hydrophobic requirement of the photosystem. This purpose-built environment provides the optimal conditions for PS1 and overcomes the kinetic limiting steps, which are found in natural leaves. This procedure yields the highest photocurrents observed to date for semi-artificial bio-photoelectrodes while the electron transfer rate exceeds by one order of magnitude the one observed in nature.
According to the researchers, this improvement increases the efficiency of our initial biophotovoltaic concept from the nanowatt to the microwatt range. In the short term, silicon-based photovoltaics will still outperform the bio-devices in terms of stability and efficiency.
The study was published in the European journal Chemistry.