Make Energy from the Sun and Raindrops with Hybrid Solar Cells

Hybrid solar cells

Hybrid solar cells

In March 2018, American Chemical Society’s journal ACS Nano researchers reported they have developed hybrid solar cells that can generate power from raindrops. For the longest time, cloudy and rainy conditions have been an obstacle to the development of the amount of electricity solar cells can create. Not only that, but for areas where it rains a lot, solar cells doesn’t seem like the best solution for energy production. But now we can make energy from both the sun and the movement of raindrops with hybrid solar cells.

Energy diagram of the donor and acceptor

Energy diagram of the donor and acceptor

Hybrid solar cells combine advantages of both organic and inorganic semiconductors. Hybrid photovoltaics have organic materials that consist of conjugated polymers that absorb light as the donor and transport holes. Inorganic materials in hybrid cells are used as the acceptor and electron transporter in the structure.

This hybrid solar cells that can produce electricty come rain or shine was developed by Chinese engineers – Zhen Wen, Xuhui Sun, Baoquan Sun and their colleagues. The hybrid solar cell uses the triboelectric effect to harvest energy from the movement of raindrops on its surface.

Triboelectric nanogenerators (TENGs) create a charge from the friction of two materials rubbing together, otherwise known as static electricity. It’s very common on clothing, particularly flexible cloth as they can harness human motion to generate electricity. This effect the hybrid solar cells uses could capture energy not only from clothing but also car wheels, floors, or touchscreens.

The Chinese engineers added two polymer layers to form a TENG on top of photovoltaic cell so that the Hybrid solar cells can tap into the motion of raindrops rolling off the tech’s surface. The top layer consists of a polymer called polydimethylsiloxane (PDMS), while the lower layer is made of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS).

To improve the performance of both PDMS and PEDOT:PSS when raindrops touched it and then fell off it, they are textured with grooves by imprinting them with the pattern from the data side of commercially available DVDs. The textured PEDOT:PSS layer acts as a mutual electrode for both the TENG and the solar cell. It’s placed between the two devices and conducted energy from the TENG to the cell, conducting energy from the former to the latter because raindrops roll off from the top layer and brought the top polymer into contact with the bottom one.

The polymers are transparent, so the hybrid solar cells could still generate energy from the sun and raindrops because the photovoltaic cell still functions. The team notes this simple design demonstrates a new concept in energy harvesting during various weather conditions.

The hybrid solar cell uses layers of two polymers to harvest energy from raindrops

The hybrid solar cell uses layers of two polymers to harvest energy from raindrops

According to the team, the device had a peak short-circuit current of about 33 nA, and a peak open-circuit voltage of around 2.14 V. That’s not particularly high, but it is enough to demonstrate that the concept works, and might be scalable. This isn’t the first time researchers have experimented with TENGs to make solar cells more useful in other weather conditions, but the team says this hybrid solar cells is a simpler design, less bulky and easier to manufacture than others.

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