Household artificial lighting cannot be compared to natural sunlight - the usual illumination level in offices and shops is in the range of 100-500 lux, while on a sunny afternoon outdoors you can get 110, 000 lux or more. But even this dim light, which has already fulfilled its function and illuminated the room, can be additionally used to generate energy. To this end, a team of scientists from the University of Tor Vergata in Rome, the Universidad Surcolombiana and the Fraunhofer Institute have developed a new type of flexible solar cells based on perovskite.
The mineral perovskite, aka calcium titanate, which was included in the TOP-10 breakthroughs of the year in 2013, has a natural atomic structure that is ideal for absorbing light. It is deposited on ultra-thin glass substrates with indium oxide and tin oxide, resulting in flexible, compact and highly efficient low-light photovoltaic cells. Or rather, the most effective today - their efficiency is at least 20%.
Most indoor PV cells have an efficiency below 10%, and although some developments show more than 26% - but only at illumination of 1000 lux. Perovskite modules in experiments reached the level of 20.6% at 200 lux and 22.6% at 400 lux. You should not expect a high power density from them, at 200 lux it reaches 16.7 μW / cm2, and at 400 lux - 35 μW. This is the energy consumption level of simple sensors, but not household appliances.
What is most intriguing is the fact that this energy is not just free, but of “secondary use”, since the operation of photocells does not affect the primary task, that is, the lighting of the premises. It turns out that we derive more benefit from the energy already spent, which, given the flexibility, cheapness and simplicity of photovoltaic cells, can significantly change the energy consumption of the future "smart home".