The principle of power generation for solar panels is to convert solar radiation into electricity, so will it be possible to generate power using indoor lighting? Indian scientists have recently developed an organic solar module made with a paper-based substrate that possesses both cost and environmental advantages, and is able to achieve a power density of 12µW/cm2 under 1000 lux, which makes it possible in providing power for small electronic equipment in the future.
The most common polysilicon solar panel cannot absorb indoor light, and has a restricted degree in absorbing spectra since the 1.1eV energy gap of silicon is merely able to absorb near infrared, visible light, and ultraviolet light below 1,000nm, whereas the wavelength for indoor visible light is at roughly 380-780nm, thus polysilicon cells often encounter inferior conversion efficiency at barely 10% after being shifted to an indoor environment.
Hence, the development of indoor solar panels is implemented in other directions that no longer adopt wafers. Take the IIT Kanpur for instance; the institute has developed a flexible solar substrate that is bendable and produces insignificant amount of rubbish using “paper”, and the research team has also developed a special depletion region that makes it possible to construct a 12x12cm2 organic solar sub-modules on top of the substrate, which has an effective area of 108cm2, and possesses similar performance to polysilicon solar panels under 1,000 lux cold light LED.
The research team primarily tested the two organic solar bundles of PTB7：PCBM and P3HT：PCBM under a standard lighting based on a total illuminance of 963.75W/m2 from an AM1.5G spectrum, where the conversion efficiency for the photosensitive layers of the two composite organic solar has arrived at 4.23% and 2.38% respectively, which the research team pointed out is the best record in efficiency for organic solar made with paper-based substrate.
Sundar Kumar Iyer, professor of electrical engineering at IIT Kanpur, commented that a power density of 12µW/cm2 (solar calculator requires about 5μW) under 1,000 lux cold light LED has a similar performance to polysilicon solar panels of 15% in conversion efficiency, since the power density of polysilicon solar panels is at 13μW under the same environment, thus the research team believes that this proves the feasibility of organic solar panels in indoor environment.
The efficiency for PTB7:PCBM and P3HT:PCB is at 6.44% and 3.37% respectively if a small sized paper-based solar substrate is used, which is also the best result on record. As pointed out by the research team, an adoption of a photosensitive layer that possesses a higher level of efficiency should be able to elevate the efficiency of organic solar panels, making it the optimal choice for both indoor and outdoor application.
(Cover photo is a sketch, source: pixabay)