The increasing variety of uses for solar cells often run into several key limitations: in its current state, the technology is still below the pale in terms of efficiency, and is (obviously) dependent on a healthy dose of direct sunlight.
One way of addressing the issue, employed in a number of research projects, is to equip the panels with a pseudocapacitor or triboelectric nanogenerator (TENG), creating a device capable of transducing the motion of raindrops into electricity.
Triboelectric nanogenerators convert mechanical friction into energy – a process known to most people as static electricity (most of which is triboelectric) – which could lead to electronics which sustain themselves by producing energy through clothing or touchscreens.
Such devices, however, are bulky, thereby shrinking the range of real-world functionality, and rather complicated to manufacture. Luckily, by building on previous research, a group of scientists from China had recently developed a clever work-around.
First, they imprinted two polymers, PDMS and PEDOT:PSS, with grooves by placing them onto commercially available DVDs, thereby adding texture to (i.e., increasing the contact area of) the TENG device.
Next, the textured PEDOT:PSS layer was sandwiched between the TENG and the solar cell to operate as a mutual electrode. The polymers themselves are transparent, allowing the photovoltaic cell to generate energy come rain or shine, albeit at a slightly lower rate.
“The biggest breakthrough in this work is that an integrated generator composed of a solar cell and a TENG was demonstrated through sharing a mutual electrode,” said co-author on the paper Zhen Wen from Soochow University.
“Compared to previous work, the simple design of the mutual electrode reduces the number of functional layers, which greatly improves the output efficiency.”
As an added bonus, the polymers also protect the silicon layer from rain, and reduce unwanted reflection of precious sunlight.
The device has been shown to have a peak short-circuit current of about 33nA, and a peak open-circuit voltage of around 2.14 V, which is not particularly high, but certainly enough to demonstrate the viability and (hopefully) scalability of the concept – a (relatively) small amount of energy produced during a rain shower is still much better than none at all.