Preparation And Property Study Of Nanostructure On The Surface Of Silicon And Gallium Arsenide

Solar cells(SCs) are still among the greatest potential options to solve energy problems. They are often divided into three generations:(1) first generation SCs referred to as crystal ine SCs,(2) second generation SCs represented by thin-film SCs, and(3) third generation SCs collectively known as high-efficiency SCs. Considering technology maturity and cost, it is an important issue to utilizing third generation technics to enhance energy conversion efficiency of first generation SCs in a long term. Improving light absorption including texturing, fabricating nanostructure and adding nanoparticles, is a significant access to high light absorption efficiency. The purpose of this paper is studying how nanostructure and nano gold particles influence the light absorption of Si and GaAs SCs. Main contents include:Firstly, nano-scale gold film was deposited on the Si and GaAs substrates with ion sputtering equipment, followed by rapid thermal annealing processing, resulting in the formation of nano gold particles on the substrates. In this part, we studied how annealing processing with different kind of conditions such as thickness of gold film, annealing time and annealing temperature influences the morphology, size and distribution of nano gold particles. Nano gold balls with spherical uniform and discrete distribution will come into being when the annealing temperature and time are set as 500°C and 30 s.Secondly, nanostructures were fabricated on the surface of Si using metal assisted chemical etching(MAC Etching) with nano gold particles as mask, silver film as catalyst. In this part, we explored the effects of different etching conditions on the formation of nanostructures. Regular nano silicon hole can be obtained after 2 minutes of etching when HF:H2O2:H2O equals 30:1:15(molar ratio) and thickness of Ag film is 22 nm.Thirdly, etching conditions of GaAs nanostructures were studied using MAC etching with nano gold balls as catalyst. To gain smooth inverted nano pyramid and hole, GaAs substrate should be immersed in etching solution of HF, H2O2 and EtOH with molar ratio 30:1:15 for 5-7 minutes.Fourthly, nano hemisphere cavity and nano gold ball were simulated independently and unitedly by finite-different time-domain(FDTD) method. Simulation showed that the synergetic enhancement of cavity and ball emerges in the scope of 400 nm- 550 nm.Finally, nano gold balls were deposited on GaAs SCs by simple and efficient “boiling deposition” technique, and then photovoltaic properties and quantum efficiency were measured. Thin film GaAs solar cell can get a 15.4% increase of energy transformation ratio using nano gold balls with a radius of 10 nm. Simulation and experiment were consistent to demonstrate the enhancement of light absorption. However, nano gold balls with a radius greater than 10 nm did not enhance light absorption due to agglomeration, which was demonstrated using FDTD simulation.