The optimizations of the emitter region and the metal grid of a concentrator silicon solar cell are il- lustrated. The optimizations are done under 1 sun, 100 suns and 200 suns using the 2D numerical simulation tool TCAD software. The optimum finger spacing and its range decrease with the increase in sheet resistance and con- centration ratio. The processes of the diffusion and oxidization in the manufacture flow of the silicon solar cells were simulated to get a series of typical emitter dopant profiles to optimize. The efficiency of the solar cell under 100 suns and 200 suns increased with the decrease in diffusion temperature and the increase in oxidation tempera- ture and time when the diffusion temperature is lower than or equal to 865 ℃. The effect of sheet resistance of the emitter on series resistance and the conversion efficiency of the solar cell under concentration was discussed.
A 16 channel arrayed waveguide grating demultiplexer with 200 GHz channel spacing based on Si nanowire waveguides is designed. The transmission spectra response simulated by transmission function method shows that the device has channel spacing of 1.6 nm and crosstalk of 31 dB. The device is fabricated by 193 nm deep UV lithography in silicon-on-substrate. The demultiplexing characteristics are observed with crosstalk of 5-8 dB, central channel＇s insertion loss of 2.2 dB, flee spectral range of 24.7 nm and average channel spacing of 1.475 nm. The cause of the spectral distortion is analyzed specifically.
A new technique to generate a millimeter（mm）-wave carrier of 32.57 GHz（f_（LO）=10.85 GHz） with single sideband modulation（SSB） for radio-over-fiber（RoF） systems is experimentally demonstrated by using stimulated Brillouin scattering（SBS）.The SSB is realized by directly amplifying the ＋3rd sideband of the modulated optical carrier in the process of SBS.The pump wave is provided through a double Brillouin scattering frequency shifting configuration.The use of the same laser source to generate the pump wave ensures the stability of the mm-wave generation system since the relative frequency shift between them can be eliminated.In addition, the mm-wave carrier obtains an RF power gain of 21 dB with the SBS amplification and a 3-dB bandwidth of 10kHz.
Ge nano-belts with large tensile strain are considered as one of the promising materials for high carrier mobility metal- oxide-semiconductor transistors and efficient photonic devices. In this paper, we design the Ge nano-belts on an insulator surrounded by Si3N4 or SiO？ for improving their tensile strain and simulate the strain profiles by using the finite difference time domain （FDTD） method. The width and thickness parameters of Ge nano-belts on an insulator, which have great effects on the strain profile, are optimized. A large uniaxial tensile strain of 1.16% in 50-nm width and 12-nm thickness Ge nano-belts with the sidewalls protected by Si3N4 is achieved after thermal treatments, which would significantly tailor the band gap structures of Ge-nanobelts to realize the high performance devices.
The silicon vertical multi-junction （VMJ） solar cell has a good potential in high concentration, but it requires high quality front and back surface passivation layers to keep its high efficiency. We try to add dopants into the front and back surfaces of the VMJ cell to release this strict requirement in this work. The effects of recombination velocities, doping types and doping pro- files of front and back surfaces on the performance of the P-type VMJ cell were calculated under 1 sun and 1000 suns. The 2D numerical simulation tool TCAD software was used. The performance of the VMJ cell without front and back surface dopants was also calculated for comparison. It was found that the requirement of high quality front and back surface passivation layers could be released remarkably by adding either N-type or W-type front and back surface dopants. For the two types of front surface dopants, the highest efficiencies of the cells were got by light dopant; for the two types of back surface dopants, the doping type and profile affected little on the performance of the cell in our calculation range. It was also found that the series resistance of the VMJ cell with N-type front surface dopant was decreased by the 2D effect of front surface emitter. The VMJ cell with W-type front surface dopant had the highest efficiency under 1000 suns and the VMJ cell with N-type front surface dopant had the highest efficiency under 1 sun in our calculation range.
