ABSTRACT
Silicon based photo voltaic panels are the mainstream of solar cells. However, there are intrinsic limitations of such devices for replacing power plants. The low conversion efficiency (<20%) would make it higher cost than generators run by fossil fuels. The repeated high temperature processes for extracting, purifying, and ingoting silicon actually wasted more electricity that may be recovered by solar cells. Additionally, silicon is not radiation hard so its crystalline structure will be gradually damaged by the bombardment of UV photons from the sun.
All these drawbacks can be overcome by using amorphous diamond as the electron generator in vacuum. Amorphous diamond contains the highest amount of atoms per unit volume (about 180/nm3). Most carbon atoms are tightly held by distorted tetrahedral (sp3) bonds. Because these distortions are all different, all carbon atoms have unique electron energies. The presence of numerous discrete energy states allows valence electrons to be excited by absorbing minute energies. Amorphous diamond is the only blackbody material that can absorb and emit low energy photons (e.g. 10 microns wavelength IR) and phonons (e.g. 100 C heat). If amorphous diamond is exposed in vacuum, the highly excited electrons can be emitted readily. Thus, amorphous diamond can be the most efficient thermionic material with the capability to convert up to half of sunlight’s energy into electricity.
Experimental data has confirmed that amorphous diamond can absorb more energy than silicon when exposed to sunlight. The conversion efficiency for generating electricity can be boosted by narrowing the vacuum gap between the energy input anode and electron output cathode. If the gap is reduced to about one micron, the conversion efficiency can be much higher than that of silicon solar cells.
