Design And Optimization Of Semiconductor Nanowire Pn Junction Photovoltaic Devices

?-? semiconductor nanowire arrays have shown great potential in the next generation of high-performance,low-cost solar cells due to their excellent antireflection ability,high lattice mismatch tolerance and small occupied area.However,due to the existence of the gap between the nanowires,the absorption loss of the substrate becomes an important bottleneck limiting the performance of nanowire array solar cells.This paper focuses on the research of GaAs nanowire array solar cells,aiming to enhance reflection at the bottom through device structure innovation,and achieve high conversion efficiency at a very small nanowire height.The main achievements are as follows:(1)The spectral absorption and photovoltaic performance of actual GaAs nanowire pin junction solar cells are studied.Studies have shown that compared with the ideal device filled with air,the actual device filled with organic polymer will enhance the reflection and decrease the absorption efficiency due to the increase of the effective refractive index.When the nanowire length is 1 ?m,the diameter is 180 nm and the D/P ratio is 0.5,the efficiency of the axial pin junction actual device is 2.1%lower than that of the ideal device.When the nanowire length is 1 ?m,the diameter is 360 nm and the D/P ratio is 0.5,the efficiency of the radial pin junction actual device is 2.34%lower than that of the ideal device.(2)A bottom-reflectivity-enhanced axial pin junction GaAs nanowire solar cell structure is proposed,and its spectral absorption and photovoltaic performance are simulated.Studies have shown that the MgF2 dielectric layer embedded between the polymer and the substrate can significantly reduce the absorption loss of the substrate and enhance the optical absorption of the nanowires,especially the intrinsic region.After structural optimization,when the nanowire length is 1 ?m,the diameter is 180 nm,and the D/P ratio is 0.5,the conversion efficiency of the device reaches 15.9%,which is 2%higher than that of the traditional structure.(3)A bottom-reflectivity-enhanced GaAs nanowire radial pin junction solar cell structure is proposed,and its spectral absorption and photovoltaic performance are simulated.Studies have shown that by replacing SiO2 between polymer and substrate with MgF2 dielectric layer with low refractive index,the absorption loss of substrate is significantly reduced.When the nano wire length is 1 ?m,the diameter is 360 nm and the D/P ratio is 0.5,the conversion efficiency of the device reaches 12.2%,which is 2.9%higher than that of the traditional structure.