Two common features are generally found with every human activity: the presence of light, either from the sun or man made sources, and the presence of fibers, such as in the clothes we wear. Now imagine if the fibers making our clothes are efficient converters of light into energy. This would not only help make individuals more energy independent, but enable scaling up of light energy harvesting products to carpets, curtains, tents, and even textile-based solar farms, as shown in the figure. One can also envision immediate impact in scenarios requiring energy sources far away from convenient locations, such as when rescue workers and the military are deployed in disaster effected or remote areas.
Our patent pending design for an ultra-light and high-efficiency solar fiber consists of making an inorganic solar cell inside hollow polymer fibers with small diameter (50-100 micron) and long lengths (1 to 10 m). Solar energy is an acknowledged source of plentiful and renewable energy that can help alleviate the need for non-renewable power. However, current generation solar harvesting techniques, even those marketed as solar fabric, rely almost completely on planar solar cell technology. However, this technology faces several limitations to continued reduction in ratio of cost to performance. In our idea, the high efficiency to convert light into electricity will come partly from the ability to capture light incident from any direction (i.e. three dimensional) and trap it with high efficiency within the hollow fiber. Our idea overcomes several other limitations of planar technology such as need for anti-reflective coatings, surface texturing, and back reflectors, and this will reduce the overall cost and complexity of materials and manufacturing. In addition, the hollow fiber design is intrinsically flexible and light weight, making it amenable to create textile of large sizes and complex shapes, unlike planar devices.
The low cost of production will come from the use of liquid deposition techniques to deposit the films of the various conducting and semiconducting materials necessary to make the electrical contacts and p-n junction, as shown in the figure. We will first optimize our design by computational modeling of light trapping efficiency and the resulting current generation based on use of inexpensive and generally earth abundant metals such as Cu, Mo, and Ag, and semiconductors such as Cu-Zn-Sn-S (CZTS) and PbS. Subsequently we will manufacture the solar textile by liquid deposition inside the fibers. Because the semiconductor materials will be encapsulated inside the fiber, there is very low risk of materials contact with the user while also making it easy to reuse and recycle the textile due to the encapsulated design.