The Opto-electronic Properties Of Phosphorus Doped Nanocrystalline Silicon Embedded In Amorphous Silicon Carbide Film Structure And Its Applications In Solar Cell Devices

The energy problem is one of the problems human beings must cover come.Compared with fossil energy and nuclear energy,solar energy is a kind of clean energy with the advantages of endlessness,environmentally friendliness and so on,providing human beings with a method to solving the energy problem.Researches on the new generation solar cells based on quantum dots are in process.Theories reveal that silicon based quantum dot solar cells will be in better uses if doped silicon carbide materials can act as a window layer.Therefore,in our experiments,the optical and electrical properties of nanocrystalline silicon embedded in amorphous silicon carbide film structures with different phosphorus doping concentrations and with different carbon silicon ratio.Besides,doped silicon carbide is also used as a window layer in silicon based quantum dot solar cells with better device performances.The main contents and conclusions are as followed:1.Hydrogenated phosphorus doped silicon carbide films are deposited on silicon or quartz substrates with plasma enhanced chemical vapor deposition techniques.The flow rate of CH4 and SiH4 is invariable while the flow rate of PH3 is changed.Dehydrogenation at 4500C and annealing at 1000oC in N2 atmosphere are carried out in turn to get phosphorus doped nanocrystalline silicon embedded in amorphous silicon carbide film structure.Compared with as-deposited samples,carbon silicon bonds are more in annealed samples and the crystallization degree is more.The optical band gap is enlarged and conductivity is increased with 6 orders of magnitude.The conductivity activation energy is decreased because of annealing.2.With phosphorus doping increasing,erystallization degree is more which demonstrates that phosphorus doping is helpful to crystallization in a degree.Meanwhile,the optical band gap is larger,the main carrier concentration is high,the conductivity is enlarged with doping increasing.The mobility is increased firstly and then decreased.After all,phosphorus doping silicon carbide films with relatively large optical band gap and high conductivity are got,which are competitive to act as a window layer in silicon based quantum dot cells.3.Meanwhile,phosphorus doped silicon carbide films with different carbon silicon ratio is prepared.It is found that with the carbon silicon ratio increasing,the optical band gap of as-deposited samples are enlarged with conductivity decreased.Crystallization degree is less and carbon silicon bonds become more with the ratio increasing.The optical band gap,mobility and conductivity is decreased gradually.The conductivity activation energy is enlarged.The main carrier concentration is firstly decreased and then increased.4.Silicon based quantum dot film solar cells in which doped silicon carbide with large optical band gap and high conductivity acts as a window layer are prepared in a plasma enhanced chemical vapor deposition system.P type silicon are used as a substrate.The deposition time of this window layer is about 5 minutes and the annealing temperature is 900?,on which condition the device performance is better.It is found that compared with phosphorus doped silicon window layer,cells with phosphorus doped silicon carbide window layer have higher open-circuit voltage and short-circuit current.The extermal quantum efficiency is enhanced in all the wavelength ranges.