Researchers have now developed extremely thin, flexible, and light solar cells that can even rest on a soap bubble.
The new cells can efficiently capture energy from light and could provide alternative means to power innovative electronic devices such as medical skin patches, for which traditional energy sources are not so perfect.
The tremendous developments in electronic skin for robots, sensors for flying devices and biosensors to detect illness are all limited in terms of energy sources. Rather than bulky batteries or a connection to an electrical grid, we thought of using lightweight, ultrathin organic solar cells to harvest energy from light, whether indoors or outdoors.
Eloïse Bihar, Postdoc, KAUST
Bihar is a postdoc in the team of Derya Baran, who headed the study.
Today, thermal evaporation or spin-coating was the technique typically used to make ultrathin organic solar cells. However, this technique is not scalable and tends to limit the geometry of the device. It also involves the use of a transparent and conductive, yet inflexible and brittle, material known as indium tin oxide (ITO) as an electrode.
To address these challenges, the researchers applied inkjet printing. “We formulated functional inks for each the layer of the solar cell architecture,” stated Daniel Corzo, a PhD student in Baran’s team.
As a replacement to ITO, the researchers printed a flexible, transparent, conductive polymer known as PEDOT:PSS, or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate. A light-capturing organic photovoltaic material was sandwiched between the electrode layers. The entire device could be concealed within parylene, which is a waterproof, flexible, biocompatible protective coating.
According to Corzo, despite that inkjet printing is highly adaptable to scale up and low-cost manufacturing, it was challenging to develop the functional inks.
Inkjet printing is a science on its own. The intermolecular forces within the cartridge and the ink need to be overcome to eject very fine droplets from the very small nozzle. Solvents also play an important role once the ink is deposited because the drying behavior affects the film quality.
Daniel Corzo, PhD Student, KAUST
Once the ink composition was optimized for each layer of the device, the performance of the solar cells was tested by printing them onto glass. The solar cells exhibited a power conversion efficiency (PCE) of 4.73%, which surpasses the earlier record of 4.1% for a completely printed cell.
Furthermore, the researchers demonstrated, for the first time, that it was viable to print a cell onto an ultrathin flexible substrate, achieving a PCE of 3.6%.
Our findings mark a stepping-stone for a new generation of versatile, ultralightweight printed solar cells that can be used as a power source or be integrated into skin-based or implantable medical devices.
Eloïse Bihar, Postdoc, KAUST
The KAUST team is inkjet printing lightweight, ultrathin organic solar cells to harvest energy from light. Video Credit: © 2020 KAUST.
Bihar, E., et al. (2020) Fully Inkjet‐Printed, Ultrathin and Conformable Organic Photovoltaics as Power Source Based on Cross‐Linked PEDOT:PSS Electrodes. Advanced Material Technologies. doi.org/10.1002/admt.202000226.