The Study On Single Hydrogenated Nano-crystalline Silicon Thin Film Solar Cells

Energy motivates the national economy. Under the pressure of energy crisis and environment deterioration, global nations develop the sustainable clear energy as the development strategy in the future. Solar cells have advantage of rich resource,no regional limitation,no-pollution and so on.Both of costs and efficiency are the main parameters to influence widespread production of solar cells. Hydrogenated nano-crystalline Silicon thin films^the new style, deserves the researchers' attentions, because of his prominent optics stability and electrical properties. The nano-structure consists of nano-crystal and amorphous content, which gets half singly. And interface area is about 2-4 atoms. This structure not only has wide optical band-gap of amorphous Silicon thin films, but high conductivity and optical stability of mono-crystalline Silicon. By now human beings have developed it as LED, tunnel diode and solar cells and so on. This paper aims at the influences of this novel structure to thin film solar cells.Firstly, nano-crystalline films have been grouped by depositing conditions, and then characterized and measured optical and electrical properties. The effect of depositing conditions on micro-structure, optical and electrical performances of the nano-crystalline films has been investigated.For intrinsic nano-crystalline Si films:1) Experiment results show that the crystal content (Xc) decreased gradually and the crystalline size increased with Silane volume increasing. When V_DC changed only, it has little effect on crystalline size, but crystal content increased from 36% to 51.4% directly. Combined with crystalline dynamics, it has been concluded direct current bias supplied the crystal with dynamics of crystallization.2) Temperature has directly influenced the crystalline size and crystal content. By experiments, it has been found that crystalline size and crystal content of nc-Si films showed an upward tendency and favored crystalline regularly growth.3) Kinetic energy of ion in reaction chamber was controlled by R.F. power, which got bigger the ion's moved more intensely. Then films' Raman spectra hadblue-shift, namely more crystallization.4) More Silane volume, more amorphous content, and E_g tended to increase; to bethe contrary, upwards direct current bias made E_g down from 2.2eV to 1.6eV.Analyzing the Raman spectra of samples, whose size differ little but X_C, it hasbeen found that when X_C increased only, E_g was downward correspondingly,which made E_g indirect control come true.P type (Boron-doped) nc-Si:H films was acted as the window layers of solar cells. Under rising Boron content only, crystal content decreased in a linear ratio by the poison of Boron to film deposition, but crystalline size and E_g came out to an irregular trend. When V_dc increased only, crystal content decreased linearly from 39.7% to 51.6%, similar to the trend of intrinsic layers. We can see that V_dc supplies power to growth of the films whether they are doped or not. Boron element, which belonged to non-carbon family, made bonds and crystal growth complicate. Especially with boron content varied, films' deposition got to complication. As a result, it needed further study about the micro-structure of P-type nc-Si:H films.On the basis of photovoltaic devices' need for optical and electrical properties, AMPS (Analysis of Microelectronic and Photonic Structure) was used to investigate the output parameters of solar cells: open circuit voltage,short-circuit current,fill factor and converse efficiency with varied I layer thickness and E_g.