Design, realization and loss analysis of efficient low-cost large-area bifacial interdigitated-back-contact solar cells with front floating emitter

Large-area (251.96 cm2) bifacial interdigitated-back-contact (IBC) solar cells are presented in this work. We employ front floating emitter (FFE) to replace the front surface field (FSF) to simplify the process sequences. A simplified process flow is exploited to fabricate the IBC solar cells through industrial equipment and compatible processes. Double side boron diffusion followed by etch-back to form the emitter and lightly doped front surface, reducing high-temperature influence on the bulk lifetime and fabrication complexity. Ion implantation and anneal process is applied for base doping. The cell conversion efficiency reaches 22.92%, independently certificated by Fraunhofer Institute for Solar Energy System CalLab (Fraunhofer ISE). The IBC solar cells feature an open metallization grid, which offers a bifacial response with the bifaciality reaches to 72%. Only one-step mask and opening procedure was used, which greatly simplified the process. These results demonstrate the feasibility of this simplified process for manufacturing low-cost high-efficiency of IBC cells. Key parameters such as surface recombination J0, metal contact recombination J0-metal, contact resistivity of the cells are extracted by specially designed structures. Loss analysis shows that further efficiency improvement can be attained though reducing the contact resistance and metal contact recombination. The results in this work indicates the potential of this novel process for producing low-cost high-efficient IBC solar cells.