Solar cells are afraid of the sun, a sun will see light to death? This sounds a bit ridiculous, but it is also true and correct fact. Back light UV photolysis, EVA discoloration, organic batteries (organic batteries, fuel sensitized batteries, Perovskite batteries) UV light photolysis, photo-induced attenuation of crystal silicon cells, and light and heat attenuation are all problems caused by light, which seriously affect the efficiency of power generation and the reliability of components. After many years of hard work by the academic community, many problems have been solved. All have become history. But often with the relentless pursuit of efficiency, new problems will come out again!
High UV light transmission module
Traditional components basically do not expect the generation of UV light. The reason is roughly as follows:
- The glass content of the component glass is relatively high, and UV light cannot penetrate the battery.
- The doping concentration of the emitter of the crystalline silicon is relatively high, forming a 'dead layer'. The short-wavelength light is highly compounded and cannot be used effectively.
But after all, the energy of ultraviolet light is very large, so people have been playing it all the time. High-transparent glass, anti-reflective glass, improved positive silver, and lightly doped emitter, make the possibility of using ultraviolet light increase greatly. So as a last resort Obstacles, people have developed high ultraviolet transmittance EVA. High permeability EVA can make the short-circuit current and the final power generation efficiency increased by 1.7%, just impressive.
Attenuation problem of high UV transmission components
However, the problem came. The researchers found that ultraviolet light has serious damage to the battery. Basically, as the injection of ultraviolet light increases, the battery's index basically decreases linearly. Among them, the drop in open circuit voltage is particularly severe.
(Witteck, PIP, 2017)
The process of finding the source of attenuation is no different from the detection of homicide:
- Light infiltration basically excludes the effect of LID;
- The light transmittance of EVA and glass has not changed, eliminating the discoloration factor, which in turn points to the material passivation;
- Established a standard diode model and found that the main factor in the drop in open circuit voltage is the increase in SRH;
- Combined with long-term reports, the basic facts have been clarified: The silicon nitride/silicon interface has been damaged, resulting in a decrease in the hydrogen passivation effect, an increase in silicon dangling bonds, and an increase in surface recombination.
- After calculation, to solve the hydrogen-silicon bond, the required light energy is just over 300 nanometers, just in the ultraviolet region. The last link of the evidence chain has finally been found: UV-induced silicon nitride passivation The drop in effect is the culprit!
According to calculations, the 'dividend' of high-ultraviolet translucent components is completely attenuated and exhausted after approximately 10 years of outdoor use. If the attenuation continues after 10 years, the lifetime gain of high-UV components will not increase. Can't say it!
Strictly speaking, this is not a postscript. After all, this is still an unsolved problem. UV, do or not? If so, how does the attenuation problem be solved? Photovoltaics is a highly innovative and highly conservative industry. Each technological innovation is often accompanied by New problems, waiting to be solved.
It is the charm of the photovoltaic industry that is moving forward through twists and turns!
