Efficient Boron Doping in the Back Surface Field of Crystalline Silicon Solar Cells via Alloyed-Aluminum–Boron Paste

Back surface field (BSF) can effectively reflect minority carriers from the back surface area of a crystalline silicon (c-Si) solar cell and therefore improves its photovoltaic performance. Aluminum BSF (Al-BSF) is presently the most widely used BSF for p-type c-Si solar cells. Due to the relatively lower solubility of Al in c-Si, it is hard to achieve a high doping concentration in the Al-BSF, which, in turn, limits the conversion efficiency of c-Si solar cells. This letter presents a technique to achieve a much higher doping concentration in the BSF by boron doping through the screen-printed alloyed-aluminum-boron paste. It was found that a lower sheet resistance was resulted in the BSF. This technique is expected to be beneficial to the improvement of conversion efficiency of c-Si solar cells.