Bifacial Heterojunction Back Contact Solar Cell: 29-mW/cm2 Output Power Density in Standard Albedo Condition

A new crystalline-Si (c-Si) solar cell design based on bifacial heterojunction back contact (HBC) with a transparent conductive oxide (TCO) is proposed by the numerical simulation method. Three bifacial HBC schemes are evaluated and compared: full-area contact with an increase in the pitch distance, point contact, and point contact with indium tin oxide (ITO). The results reveal that point contact with ITO is the most optimal among the three aforenoted schemes. The bottleneck of bifacial HBC is caused by the extremely low carrier mobility in an amorphous Si (a-Si) region, and this can be resolved by applying ITO to form a full-contact area that covers all surfaces of the a-Si region. A maximum power density of 29 mW/cm ² is obtained from bifacial HBC, which is an extremely high output from a single-junction c-Si solar cell. The improvement in the maximum power density over the monofacial condition is 8% at 20% albedo.