Sanyo´s Challenges to the Development of High-efficiency HIT Solar Cells and the Expansion of HIT Business

The world´s highest conversion efficiency levels of 21.8% (V_oc: 0.718 V, I_sc: 3.852 A, FF: 79.0%, confirmed by AIST) with a practical size of 100.4 cm² has been achieved by using the HIT (hetero-junction with intrinsic thin layer) structure. This high efficiency has been mainly realized by the excellent c-Si/a-Si hetero-interface property obtained by our optimized surface cleaning process and high-quality and low-damage a-Si deposition technologies. This excellent c-Si/a-Si hetero-interface of the HIT structure results in a relatively high open circuit voltage (V_oc) over 710 mV. Recently, we have succeeded in achieving an outstanding V_oc of 730 mV for other efficient HIT solar cells. This result indicates the possibility of further improvement in the conversion efficiency of HIT solar cells. The higher V_oc results in not only a higher conversion efficiency but also an improved temperature coefficient, which is another practical advantage for outdoor use