Organic Solar Cells
By Izabela Ninu
Paper-based BPVs (microbial biophotonics) are not meant to replace conventional solar cell technology for large-scale power production, but instead, could be used to construct power supplies that are both disposable and biodegradable. Their low power output means they are more suited to devices and applications that require a small and finite amount of energy, such as environmental sensing and biosensors.
Organic solar cells (OSCs) are a type of photovoltaic that uses organic electronics, a branch of electronics that deals with conductive organic polymers or small organic molecules, for light absorption and charge transport to produce electricity from sunlight by the photovoltaic effect.
The molecules used in organic solar cells are solution-processable at high throughput and are cheap, resulting in low production costs to fabricate a large volume. Combined with the flexibility of organic molecules, organic solar cells are potentially cost-effective for photovoltaic applications.
However, the main disadvantages associated with organic photovoltaic cells are low efficiency, low stability, and low strength compared to inorganic photovoltaic cells such as silicon solar cells. Despite these challenges, in 2023, a new record-breaking efficiency of 19.3% was achieved by Hong Kong Polytechnic University.
Cyanobacteria in OSCs
Cyanobacteria are an ancient group of photoautotrophic prokaryotes (photoautotrophs are cells that capture light energy, and use carbon dioxide as their carbon source), and play an essential role in the global carbon cycle. They are also model organisms for studying photosynthesis and circadian regulation, and metabolic engineering and synthetic biology strategies grant light-driven biotechnological applications to cyanobacteria.
Furthermore, significant advances have been made with genome editing in several cyanobacteria strains. For instance, the CRISPR-Cas12a vector has been developed for genetic manipulations in cyanobacteria. This technology has the potential to improve the editing processes using the Cpf1 nuclease in cyanobacteria. Cpf1, also known as Cas12a, is a novel RNA-directed dsDNA nuclease that has been used in cyanobacteria for genome editing1. It is an alternative to the commonly used Cas9 nuclease in CRISPR technology)
As Cyanobacteria are photosynthetic microorganisms that can produce organic compounds using solar energy, they have been found to create micro bio-solar panels that can retain an electrical charge.
Scientists have discovered a way to create bio-solar cells with cyanobacteria using an inkjet printer and carbon nanotubes. The photosynthesis of cyanobacteria can generate electricity, making it ideal for low-power or temporary devices. In one study, European scientists from Imperial College London, University of Cambridge, and Central Saint Martins were able to create a battery and bio-solar panel with cyanobacteria. The cyanobacteria were still alive after being printed with carbon nanotubes on a piece of paper using an inkjet printer.
These bio-solar panels work by having two electrodes separated inside the chamber that the cyanobacteria are printed on. When oxygen is created in the anode side, it’s released from the cathode section. Protons then move toward the cathode, where electricity is generated and water is formed.
While this process could not replace traditional photovoltaic cells due to their low energy production and short lifespan, these bio-solar panels could provide a temporary power solution in the future. It’s anticipated that they can create these micro-panels to the size of a standard 8.5-by-11 piece of paper.
Genetically Engineering Cyanobacteria
The integration of genetically engineered cyanobacteria into OSCs could enhance the performance of these cells. For example, specific base pair changes were done in the P R40 promoter at the TATAAT site and between the − 10 element and transcription start site (for the purpose of designing a new promoter, that would be stronger than the normal one. (In genetic engineering, a promoter is a sequence of DNA that initiates the process of transcription, which is the first step in gene expression. By changing the base pairs in the promoter region, scientists can control the level of gene expression))
By genetically engineering cyanobacteria to optimize their photosynthetic efficiency, it can be possible to increase the amount of electricity they can generate when incorporated into OSCs. Moreover, the use of self-replicating plasmids in cyanobacteria could potentially increase the copy number of these plasmids, thereby enhancing the overall efficiency of the bio-solar cells.
