Research On The Fabrication And Performance Of The Key Materials Of Silicon-based Quantum Dot Heterojunction Solar Cells

With the decrease of traditional fossil energy storage and accompanying increase of serious environmental pollution arising from the consumption of fossil energy,development of new forms of energy has become a consensus of world energy development.Among a variety of new kinds of energy,solar energy revolutionizes the constituent of new energy sources.This paper focuses on the research of the key materials of a new type of silicon-based heterojunction quantum dot solar cells.In this solar cell,we utilize p-type single crystal silicon as a substrate,nanocrystalline silicon thin film as an intrinsic layer,n-type silicon quantum dots embedded in an amorphous silicon carbide matrix as a window layer,as well as ZnO nanorod arrays(NRAs)as an antireflective layer.In order to fabricate the designed solar cells,the experimental research of the thesis is as follows:1.We have prepared a series of silicon-rich amorphous silicon carbide thin films by plasma-enhanced chemical vapor deposition system(PECVD).Structure and properties of these thin films were studied under different RF powers and annealing temperatures.Through a variety of advanced facilities to characterize the structure and properties of thin films,it is found that with the increase of RF power,thin film crystallization rate and grain size of silicon quantum dots decrease,while optical band gap of thin films increases.In addition,when the annealing temperature is 800 ?,amorphous phase in thin films occupies a large part.However,when the annealing temperature increases to 900 ?,much of the amorphous phase in thin film gradually transforms into crystalline phase.When the annealing temperature reaches 1000 ?,grain size becomes large and thin film optical band gap decreases.2.We have prepared a series of hydrogenated nanocrystalline silicon films under different RF powers by PECVD.Through a variety of advanced facilities to characterize the structure and properties of thin films,it is found that with the increase of RF power,both the grain size and the crystallization rate of thin film decrease.This is because the increased RF power accelerates the ionization of reactive gas,increases the deposition rate of thin films,and therefore decreases the critical nucleation free energy,which gives rise to the decrease of critical nucleus size of thin films.3.In this work,we have employed a simple and cheap chemical bath deposition method to prepare ZnO nanorod arrays and fabricated three types of polycrystalline silicon solar cells to investigate the antireflective performance of ZnO NRAs.Through a variety of advanced facilities to characterize ZnO NRAs,it is found that he synthesized ZnO NRAs feature a perfect crystalline wurzite structure and have a preferential growth along[0001]direction.The photovoltaic conversion efficiency increases from 2.27%for the polycrystalline silicon solar cells without using any antireflective layer to 6.61%for the polycrystalline silicon solar cells using ZnO NRAs as an antireflective layer.Through experimental comparison,we find that ZnO NRAs have a very good antireflective effect.