Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Si-based thin film solar cells suffer from a rather low efficiency. This leads to a relative small market share, although their module prices are comparably low. RainbowEnergy aims at a novel nanostructured Si-based thin film PV cell absorber, which increases the efficiency substantially without increasing the module costs.
If after phase separation SiOx --> 0.5SiO2 + (1-0.5x)Si the volume fraction of Si exceeds ~30%, then Si forms a percolated nanowire network. Energy-Filtered Transmission Electron Microscopy (EFTEM) studies show that nanowires have diameters of a few nanometers with a narrow distribution. This is in excellent agreement with large-scale simulations based on kinetic Monte-Carlo.
As the wire diameters coarsens with time of heat treatment like d~t1/3, and because the Si bandgap opens for nm-structures by quantum confinement, a band gap engineering for PV cell optimization becomes feasible. It will be shown that up-scaling of the nanotechnology described above to large-scale PV cell production is under way with industrial partners.