A Novel Solar Cell Ionotronic Energy Pathway Inspired by an Electric Eel

Abstract

Solar cell technology can be one of the best choices for sustainable future energy. Solar energy conversion strategies inspired by nature can play a vital role in solving the significant challenges in solar cell products such as low power conversion efficiency, expensive fabrication process, and materials. In this thesis, we introduce for the first time a solar cell with unique ionotronic technology inspired by an electric eel with a completely novel configuration of hydrogels. This new generation of solar cells utilizes an ionotronic gradient energy pathway which can greatly enhance the efficiency of solar energy collection using mobile ions. This new solar cell is made of a heterogeneous multi-layer hydrogel that mimics the artificial electric eel with the ability to produce relatively large voltage under external stimulation. Device physics, design, fabrication, and optoelectronic characterization of hydrogel solar cell devices are provided in this thesis. An artificial electrocyte was designed by using polyacrylamide hydrogel synthesized with four different components. The fabricated artificial electrocyte showed 150-180 mV for one cell containing high salinity, cation-selective, low salinity, anion-selective, and high salinity hydrogels. Seven series of these tetrameric gel cells showed 1.27 mV and 2.87 µA by the electromotive force of ionic gradient between low salinity and high salinity gels. By stacking three series gel cells in parallel, about 7 µA is reported. It is shown that the thickness of the gels has a proportional relationship with the resistance of the gels. UV-Vis spectroscopy results show that the high salinity gel is able to absorb light by a maximum peak at 534 nm for 1.5 mm of thickness. The photoconductivity tests prove the designed electric eel-inspired solar cell is able to generate photocurrent. By merging the artificial electrocyte ionic energy pathway and the principles of solar energy converter, the bio-inspired eel solar cell shows 5.08 % power conversion efficiency using three layers of low salinity/high salinity/low salinity hydrogels. The current density of 6.475 mA/cm2 is obtained for cation-selective/high salinity/anion-selective hydrogel-based solar cell. For the first time, in this project, not only new materials with exceptional properties have been introduced to the photovoltaic solar systems, but also a novel flexible, eco-friendly solar cell with a unique configuration has been proposed.