Household artificial lighting cannot compare with natural sunlight – normal light level in offices and shops is in the range of 100-500 Lux, whereas at solar noon on the street to 110 000 Lux and more. But this dim light, which has already fulfilled its function and illuminated the room, you can optionally use to generate energy. To do this, a team of scientists from the University of Tor Vergata, Rome, Universidad Surcolombiana and the Fraunhofer Institute have developed a new type of flexible solar cells based on perovskite.

The mineral perovskite, he is a titanate of calcium, which in 2013 brought in TOP 10 breakthroughs of the year, has a natural atomic structure, ideal for light absorption. It is applied on a substrate of ultra-thin glass with the addition of indium oxide and tin, resulting in a flexible, compact and highly efficient photovoltaic cells for low light. Or rather, most effective for today – their efficiency is not less than 20 %.

Most photovoltaic cells for indoor have efficiency below 10%, and although some research shows more than 26 % but only at an illumination of from 1000 Lux. Perovskite modules in the experiments reached the level of 20.6 % at 200 Lux and 22.6 % at 400 Lux. Do not expect from them a large power density, with 200 suites, it reaches to 16.7 µw/cm2, while 400 Lux is 35 µw. This level of power consumption of simple sensors, but not household appliances.

Most intriguing is the fact that this energy is not just free, but “secondary use”, as the work of solar cells does not affect primary task, that is the lighting. It turns out that we extract more benefits from the already spent energy that given the flexibility, cheapness and simplicity of solar cells can significantly change the consumption of the future “smart home”.
Source — Fraunhofer Institute