Research On Preparation And Properities Of HIT Solar Cells

The goal of photovoltaic researches is development of solar cells with stability andhigh conversion efficiency at low cost, HIT solar cells combine the high efficiencypotential of wafer-based photovoltaics and low cost of thin film solar cells, become a hotpoint in the field of photovoltaic research. In this thesis, experimental investigations on thedeposition of p-type a-Si:H thin film materials with RF plasma enhanced chemical vapordeposition technique and its application in HIT solar cells were presented. The study ofamorphous/crystalline silicon interface passivation was also investigated. In detail, thefollowing studies have been conducted:1、 In this work, RF-PECVD technique was used to grow p-type a-Si:H thin filmmaterials on slide glass and monocrystalline silicon using SiH4and B2H6as reactiongases and H2as diluent gas. The influence of silane concentrations, boraneconcentrations, heating temperatures, RF powers on deposition rate, electrical, opticaland structural properties of p-type a-Si:H thin films was studied. The results indicatedthat deposition rate increase with the increase of deposition parameters; and darkconductivity showed the similar regular, however, with the increase of RF power thedark conductivity first increases and then decreases; the optical bandgap increases withthe decrease of borane concentrations, heating temperatures and RF powers, and theincrease of silane concentrations; good microstructure p-type a-Si:H thin films can beobtained in the condition of high silane concentration, moderate borane concentrationand heating temperature, low RF power. The thin films with deposition rate of0.16nm/s,dark conductivity of8.5E-6S/cm and optical bandgap of1.73eV have beenmanufactured after deposition parameters were optimized.2、 The influence of hydrogen plasma treatments and deposition parameters ofintrinsic amorphous silicon layers on amorphous/crystalline silicon interface passivationwas studied for HIT solar cells. The results indicated that the Voc of HIT solar cellincreases with hydrogen plasma treatment time until40s and then decreases, indicatingan optimum time of~40s; the Voc decreases with the increase of RF power duringhydrogen plasma treatment; unintentional epitaxial growth was found to occur rathereasily in a plasma deposition process when the heating temperature is high and RF power is low, and it leads to the large reduction in Voc; the influence of depositionpressures on the Voc of HIT solar cell is less.3、 Through the thickness analysis about amorphous thin films, the thickness ofthe intrinsic and p-type a-Si:H layers were4nm and10nm respectively. The Voc of HITsolar cells were about0.55V, and the passivation quality and repeatability was good. Bythe measurement of QE and J-V of HIT solar cells, the results indicated that the shortwavelength response degrades severely as the a-Si:H layers thickness increases. In thisthesis, the HIT solar cells with conversion efficiency of14.77%(Voc=0.568V,Isc=37.01mA/cm2,FF=0.703) have been fabricated after deposition parameters wereoptimized.