High-efficiency c-Si based interdigitated point contact back heterojunction solar cells

We report on the modeling and performance optimization studies of point contact back heterojunction (BHJ) solar cells. BHJ solar cell technology is a combination of front heterojunction (a-Si:H/c-Si) solar cell technology and interdigitated back junction c-Si solar cell technology. In this work, both emitter (p⁺-a-Si:H) and back surface field (BSF, n⁺-a-Si:H) were formed at the rear side as an array of interdigitated points, where their respective contacts formed an interdigitated pattern. The gap between p-type and n-type contact fingers was fixed at 10 µm. The n⁺-a-Si:H (i.e. BSF) circular diameter was fixed while emitter size was varied, and vice versa. Simulation was also performed with and without passivation layer underneath emitter and BSF. We also investigated the impact of surface texture size on cell efficiency. By varying surface texture size, viz. pyramid height and base width, an efficiency as high as 26.61% was obtained with 761 mV V_oc, 41 mA/cm² J_sc, and 84.5% FF for a small pyramid structure with 2 µm height and 4 µm base width.