Solar energy conversion
Introduction
Energy and energy consumption are a serious problem of contemporary society, science and technology. Great hopes are placed in so-called solar cells, which convert solar energy into electricity. It seems that rightly so, because approximately 750 joules of energy fall on 1 m2 every 1 s in our latitudes (with perpendicular impact). By effectively converting it into electricity, we could significantly improve the current energy situation. Practically only semiconductors are suitable as transformers of this energy into electricity, because they have ideal conditions for light absorption. However, absorption alone would not solve the problem. If an electric voltage is to be generated, the carriers released by the absorbed light, i.e. electrons and holes, must be separated from each other. This can be done by the electric field present in the PN junction, which is why a semiconductor with a PN junction seems to be a very suitable element from this point of view. This is used by semiconductors made of inorganic materials such as Si, GaAs, CdTe, CuInSe2. Solar cells are also prepared from organic materials such as poly3-hexylthiophene (P3HT), PTB7 or MEHPPV, where so-called excitons (electron-hole pairs) are created by illumination. The efficiency does not reach the value of silicon, but the technology of their preparation is simpler and cheaper. The material savings are also significant, usually only very thin layers of around 100 nanometers are sufficient. Cells based on a hybrid combination of organic and inorganic components – perovskites, which promise high efficiency, are also coming to the forefront of research. However, there is currently a problem with their stability.