Research On Light Trapping And Electrical Properties Of Micro And Nano Structures In Silicon Solar Cells

Amorphous silicon is not able to fully absorb incident photons due toits thin thickness, so to increase the surface light transmittance and the bodyabsorption by enhancing the incident light path can be a vital method toimprove the final efficiency except the way of optimizing materials.Geometry of the surface and body in the form of a two-dimensionalphotonic crystal array has a good effect on light trapping and lightdispersion to improve the absorption of amorphous silicon. This paper alsostudied single crystalline silicon cells, in which the interdigital pn junctioncan modulate the current in the two-dimensional direction to improve thecell efficiency.This paper proposed two structures to study the light trappingcharacteristics on top ITO layer of amorphous silicon thin film cell, one ofwhich is making grating structureon aplane ITO layer, such as rectangular,trapezoidal, concave or convex circular ducts, to acquire the optimizedstructure with high transmittance and haze value by adjusting structuralparameters. Another approach is to deposit ITO layer on a structuredsubstrate, so the structure of ITO is equivalent to the substrate as convex arc,conclave arc or quasi-sinusoidal structure. Simulate the incident lightmodulating effects of each structure using rigorous coupled-wave analysismethod and finite difference time domain method. Get the transmissioncharacteristics of each structure and optimize them. The optimizedstructure in simulation is concave arc film structure of which the lighttransmittance is above85%and haze value above90%, while the radius of curvature equals to0.3um and period equals to0.55um. In0.73-0.83umwavelength band, the haze value is more than97%.Study the effect on electrical properties of micro and nano structuresin single crystalline silicon solar cell and propose interdigital pn structure.Adjust structural parameters such as comb depth, width and period to findthe final cell efficiency trends. And the comb terminal with round angles isfound more preferably than that of righted angles to prevent the current togather at the edge. Optimized rounded-angle interdigital structure got thehighest efficiencyof9.25%in the period of23um, depth of30umand widthof1um. Compared with corresponding planar pn junction, the finalefficiency raises about0.6%.