Stanford University develops new TMD material to help create ultra-thin, lightweight solar cells

　　A race is underway in the solar energy field: to create very thin and flexible solar panels for use in areas such as electric vehicles. A group of photovoltaic materials developed by Stanford University researchers reportedly achieved record efficiency.

　　(Photo credit: Stanford University)

　　The main advantage of these Transition Metal Disulfides (TMD), over other solar materials is the ability to efficiently absorb sunlight that hits the surface. Imagine a solar array mounted on top of the wing of an autonomous drone that is 15 times thinner than a piece of paper," said Koosha Nassiri Nazif, a PhD scholar in electrical engineering at Stanford University. That's where the promise of TMD lies."

　　For flexible, lightweight and high-power applications, such as wearables and sensors, or aerospace equipment and electric vehicles, the material of choice for solar energy today is silicon, which is too bulky and not easily bendable, so there is a strong need to find new materials.

　　Despite the promise of TMD, however, it has been difficult to convert more than 2% of the sunlight it absorbs into electricity during research experiments to date. In the case of silicon solar panels, the figure is closer to 30%. In order to promote widespread use of TMDs, this gap must be closed.

　　The new prototype from Stanford University achieves an electrical conversion efficiency of 5.1%. It is expected that with optical and electrical optimization, it can actually achieve an efficiency of 27%, comparable to the best solar panels (including silicon) currently on the market.

　　In addition, the power-to-weight ratio of the prototype is 100 times higher than similar products developed previously. This ratio is significant for mobility applications such as electric vehicles and drones, as well as the ability to charge expeditionary devices while on the move. Considering the specific power, a measure of the solar cell's electrical output per unit weight, the prototype has 4.4 watts per gram, comparable to other current thin-film solar cells, including other experimental prototypes.

　　The researchers believe that this critical ratio can be increased by a factor of 10 more through optimization. The practical limit for TMD cells is estimated to be 46 watts per gram.

　　The biggest advantage of this research is the ultra-thin thickness, which not only reduces material use and cost sufficiently, but also makes TMD solar cells lightweight and flexible enough to be molded into irregular shapes for car roofs, airplane wings or the human body.

　　TMD cells, when fully assembled, are less than 6 microns thick, about the thickness of a thin garbage bag, and require 15 layers to reach the thickness of a sheet of paper. TMD also offers other engineering advantages, such as long-term stability and reliability, and does not contain toxic chemicals. It is also biocompatible and can be used in wearable applications that require direct contact with human skin or tissue.

　　TMDs also have some drawbacks that compromise their performance. For example, the process of transferring an ultra-thin TMD layer to a flexible support material often damages the TMD layer. But this is not an insurmountable difficulty.

　　Researchers say TMDs are powerful, flexible and durable. In the field of solar technology, it is a promising new development.

　　Lithium-ion batteries (LIB) have become the main energy storage solution in the life of modern society. Among them, lithium iron phosphate batteries perfectly replace lead-acid batteries, more is the first choice for grid-connected peaking, off-grid energy storage, photovoltaic energy storage, UPS, data centers and other industries.

　　Solar power system with lithium battery energy storage system is a very promising clean energy.