We make fine silicon solar cell threads in the size of the hair that are flexible to bend. The solar cell threads can be embedded in variety of substrates. By choosing appropriate substrate we can customize solar cell products for different applications with unique features.
The solar threads can be folded up to radius of 5mm. Therefore, flexible solar cell films can be realized that can be incorporated in a variety of shape and design.
An array of solar threads can be embedded in a transparent substrate to form a partial transparent film. High crystalline solar grade silicon in solar threads efficiently convert light to electricity while the rest of the area is open for the light to cross over.
High efficiency over wide range of incidence angles
This feature is due to cylindrical symmetry in the shape of the solar threads of high crystalline solar grade silicon. If the solar threads are embedded in a transparent substrate, the final product can convert both inside and outside light to electricity.
The solar threads are fabricated by the well-developed fiber drawing method that inherits low cost and high throughput.
Long life time
In principle, solar threads has the same life time as conventional silicon solar panels.
Silicon solar panels are the most dominant commercial solar cells in the market. High efficient silicon solar cells demand a high-quality silicon crystalline which leads to high cost. Solar cells made from lower quality amorphous silicon are cheaper but have low efficiencies per unit of area. The low efficiency of amorphous silicon solar cells is due to their short carrier life time. This problem can be overcome by micro/nano structuring the surface of the silicon. Unfortunately, the upscaling of most proposed structuring methods is costly.
Our collaborative group at NTNU has developed a technique to upgrade silicon to solar grade at very low cost. In this method, the granular silicon is loaded into a cylindrical glass preform and bring to softening point of the glass. The glass is then drawn to small diameter fiber typically 1/100 of the original size and the silicon core follows the glass cladding.
It is based on well-developed optical fiber drawing method that has high throughput at very low cost. This method reduces the fabrication cost significantly due to utilization of low quality material and less material per volume and not wasting any silicon material. The solar threads benefit from short carrier paths in the range of 10-50 µm that is the natural length scale for efficient carrier collection in solar grade silicon.
Solar cell window shade
The flexibility of our fine solar threads allows us to incorporate them in a variety of window shade design. These window shades are flexible and partially transparent and efficiently convert both inside and outside light to electricity. They feature high efficiency over wide range of incidence angles and long life time.
A wide range of substrates are compatible with our solar threads due to the low temperature processing. This allow us to adapt our solar cells to any shape and environmental condition.
The solar threads embedded in flexible substrate can be used for affordable tents that efficiently convert both inside and outside light to electricity.
The solar threads are compatible with many composites that are used for cars, trains or aircrafts.
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