The Simulation Of Silicon Solar Cells And The Analysis Of Critical Physical Problems

Nowadays,with the increasing shortage of fossil fuels,solar energy,a kind of renewable energy,has been widely used in aerospace,industry and agriculture,communication,domestic solar power supply and other fields.There are several kinds of solar cells and among them silicon based solar cells are the most widely used.The fabrication of traditional silicon solar cells has become increasingly mature.However,the acquisition of key performance parameters(the front and the back surface recombination velocities Si and S2)of silicon solar cells and the critical physical problems of silicon solar cells with new structures need to be further studied.There are two aspects studied in the paper:(1)The determination of the front and the back surface recombination velocity Si and S2:The QSSPC(Quasi-steady-state Photoconductance)measurements of four samples with different front and back surface conditions are first carried out under the short wavelength illumination.Then the time-dependent distribution of excess charge carriers can be obtained under the measurements on both the front and the back sides.Based on the novel analysis method and Matlab program,Si and S2 can thus be obtained by the fitting of the curves of excess charge carriers.(2)The study of the effect of asymmetrical distribution of defect states at the hetero-interface of HH(Homo-heterojunction)n-type silicon solar cells(ZnO/(p)a-Si:H/(p)cSi/(n)cSi/(i)a-Si:H/(n)a-Si:H/Ag):The software AFORS-HET(Automat For Simulation of Hetero structures)is used in the simulation.By changing NitA/NitD=1/9,1/4,1/1,4/1 and 9/1,the influence of asymmetrical distribution of acceptor(NitA)and donor(NitD)defect states is also studied.The results are shown as follows:(1)Based on the novel analysis method and the fitting of time-dependent excess charge carrier curves,Si and S2 of four samples are determined as follows:S1=837±33 cm/s,S2=2862±114 cm/s;S1=1230±49 cm/s,S2=2998±119 cm/s;Si=24331±973 cm/s,S2=1250±50 cm/s;Si=27203±1088 cm/s,S2=24630±985 cm/s.(2)First,the(p)cSi layer introduced in ZnO/(p)a-Si:H/(p)cSi/(n)cSi/(i)a-Si:H/(n)a-Si:H/Ag solar cell has a higher tolerance for the asymmetrical distribution of the defect states at the hetero-interface,so the performance of HH solar cells is better than that of the traditional heterogeneous junction solar cells.Secondly,only when Nit is large enough,the asymmetrical distribution of Nit can have an impact on the short-circuit current density Jsc.In addition,when NitA dominates,Jsc will increase,but the open-circuit voltage Voc and the photoelectric conversion efficiency Eff will decrease.It is also found that there exists a threshold thickness of emitter,corresponding to the highest Eff.Finally,the doping concentration of emitter also has an nonnegligible influence on the performance of HH solar cells.