背面钝化晶体太阳能电池铝浆局部背电场性能研究

首先制备了4款不同玻璃粉添加量的背钝化铝浆样品,并在工业链式快速烧结炉上与背银和正银共烧得到背面钝化晶硅太阳能(PERC)电池片,然后采用扫描电子显微镜(SEM)、电阻测试仪以及电池片效率分选机对电池片样品进行表征,探讨了玻璃粉添加质量分数、烧结温度以及印刷单耗对局部铝掺杂背电场(L-BSF)厚度和效率的影响。结果表明:随着玻璃粉添加质量分数增加或烧结温度升高,L-BSF层厚度增大,转换效率和开路电压均先增大后降低,当玻璃粉添加质量分数为1.2%时样品的转换效率最高,达21.6%;当烧结峰值温度为780℃时,样品的转换效率最高,达21.4%;随着印刷单耗增大,转换效率先增加后降低,开路电压降低,L-BSF层厚度基本不变,当印刷单耗为0.18 g时,样品的转换效率最高,达21.6%。

一种有效保留图像细节的自适应图像消噪方法

针对更多保留图像细节信息有效滤除噪声的问题,分析了双密度双树复小波的变换原理及特点,推导了双变量萎缩函数,提出一种基于双密度双树复小波变换的局域自适应图像消噪算法。首先对含噪图像进行双密度双树复小波分解;后根据小波系数的统计特性以及层内和层间系数的相关性,采用结合局域方差估计的双变量萎缩函数对小波系数进行处理,并用处理后的小波系数重构图像。实验结果表明:该算法在滤除噪声的同时可保留更多的图像细节,极大地改善了图像的视觉质量。

Influence of atomic layer deposition Al_2O_3 nano-layer on the surface passivation of silicon solar cells

A stack of Al2O3/SiNx dual layer was applied for the back side surface passivation of p-type multi-crystalline silicon solar cells, with laser-opened line metal contacts, forming a local aluminum back surface field （local Al-BSF） structure. A slight amount of Al2O3, wrapping around to the front side of the wafer during the thermal atomic layer deposition process, was found to have a negative influence on cell performance. The different process flow was found to lead to a different cell performance, because of the Al2O3 wrapping around the front surface. The best cell performance, with an absolute efficiency gain of about 0.6% compared with the normal full Al-BSF structure solar cell, was achieved when the Al2O3 layer was deposited after the front surface of the wafer had been covered by a SiNx layer. We discuss the possible reasons for this phenomenon, and propose three explanations as the Ag paste, being hindered from firing through the front passivation layer, degraded the SiNx passivation effect and the Al2O3 induced an inversion effect on the front surface. Characterization methods like internal quantum efficiency and contact resistance scanning were used to assist our understanding of the underlying mechanisms.