化学腐蚀法多晶硅选择性发射极太阳电池特性研究

CHARACTERIZATION OF MULTI Si SELECTIVE-EMITTER SOLAR CELLS BY WET CHEMICAL METHOD

选择性发射极(SE)太阳电池是提高效率、降低成本的一种有效手段。采用酸性腐蚀液腐蚀发射层,对腐蚀特性和腐蚀后发射层的特性进行表征,并结合丝网印刷保护性浆料,在多晶硅上成功实现了选择性发射极太阳电池。研究结果表明,腐蚀速率基本不变,腐蚀后表面形貌无变化,腐蚀后发射层SiNx钝化效果先提高后降低,在表面浓度约为2.5×1020cm-3情况下表面复合速率最低。采用湿法化学腐蚀多晶SE电池,开路电压提高4mV,短路电流密度提高0.58mA/cm2,光电转换效率绝对值提高0.2%。化学腐蚀法工艺步骤中只有一次热处理过程,热耗小,对硅片无损害,化学腐蚀去除死层,蓝光波段响应高,钝化效果佳,特别适用于多晶SE电池。

Acid etching solution was utilized to etch emitter for multi Si wafer. The properties of both etch back process and the emitter after etch back were characterized. The SE solar cells on multi wafer have been fabricated successfully by using etch back process after screen printing etch resist paste. The analysis show that the rate of etch back is constant while the increase of sheet resistance depends mainly on the phosphorous doping profile. After etch back, there is no change for the surface topography, thus the reflectance remains the same. The passivation by SiNx improved fist and then decayed with etching back process. The surface recombination velocity is the lowest for the surface concentration of 2.5×10^20cm^-3. The removal of surface inactivated p-doped layer by the etch-back re- flects to Jsc and Voc improvement about 0.58mA/cm2 and 4mV respectively on the multi SE solar cells compared with homogeneous emitter solar cells, thus the efficiency improves about 0.2% absolutely. There is only one thermal step for etch back SE process, thus the consumption of heat is low. And there is no degradation during the process. The etch-back process is especially suitable for multi SE solar cell.