Self-charging biosupercapacitors (BSCs) that can store energy and be self-charged via chemical or solar energy conversion through bioreaction have recently attracted considerable attention. As human sweat also contains a high concentration of lactate biofuel, the harvesting and storage of the bioenergy in sweat holds the potential to provide the power for wearable electronics.
However, materials utilized in previous BSCs are either bulky, rigid, or fragile, and therefore cannot serve as suitable candidates for stretchable conformal wearable electronic devices. For a wearable BSC, the flexibility, stretchability, and skin conformity of the device are of considerable importance.
Prof. Joseph Wang’s group in UC San Diego demonstrates the first example of an all-printed dual-functional stretchable and wearable BSC, fabricated on top of low-elastic modulus and adhesive elastic films, to harvest and store energy from sweat while maintaining intimate contact with the human skin.
This wearable hybrid device, functioning as both a biofuel cell and a supercapacitor, is demonstrated to deliver high-power pulses and be rapidly self-recharged using enzymatic oxidation of lactate biofuel from human perspiration.
This work enabled material-level integration of both functionalities on the same set of electrodes, thus reducing the system complexity and minimizing the device footprint.
Discover AlsoThe new method of making mixed halide-perovskites results in solar cells with improved stability and performance. The new method results in better control over perovskite crystallization rates. This means the crystal structure is more ordered, in part due to researchers understanding and taking advantage of the faster crystallization of bromide relative to iodide.
The result is a material with fewer defects and less halide migration and thus less segregation of the bromide and iodide. This in turn means uniform mixing of bromide and iodide across the material, which allows the material to absorb light evenly. The end result is that solar cells made using the new method will perform better under real-world conditions.
Typical halide perovskite solution deposition uses an anti-solvent drip procedure to initiate crystallization of the halide film. The standard anti-solvent method for producing bromide-iodide mixed halide perovskite films often leads to excessive defect formation (e.g., bromide vacancies) owing to the rapid crystallization of bromide vs. iodide-perovskite phases. Simulations show that halide migration is enhanced in the presence of a large population of halide vacancies. This limits the stability of bromide-iodide mixed halide perovskites under light and heat.
In comparison to the anti-solvent approach, the gentler gas-quench method better controls crystallization, first producing a bromide-rich surface layer that then induces top-down columnar growth to form a gradient structure with less bromide in the bulk than in the surface region. The anti-solvent method does not produce such a gradient structure.
In this study, researchers from the National Renewable Energy Laboratory, the University of Toledo, and the University of Colorado Boulder demonstrated that the gas-quench method also produces fewer bromide vacancies and results in materials with a higher quality opto-electronic performance. Solar cells made using the gas-quench method retain desirable light absorption properties and provide enhanced performance in the form of a higher charge carrier mobility, higher open circuit voltage, and enhanced stability.
