Factors Affecting the Performance of HJT Silicon Solar Cells in the Intrinsic and Emitter Layers: A Review

Recently, the focus of solar cell research has shifted from Passivated Emitter and Rear Cell and Passivated Emitter and Rear Locally-diffused solar cells to Heterojunction with Intrinsic Thin Layer solar cells. Compared to the already mass-produced Passivated Emitter and Rear Cell and Passivated Emitter and Rear Locally-diffused solar cells, the passivation with the intrinsic thin layer of amorphous on the wafer surface, the continuous improvement of the emitter thickness, and doping concentration have enabled Heterojunction with Intrinsic Thin Layer solar cells to obtain open-circuit voltage above 750 mV while maintaining a short circuit current density of ~ 40 mA/cm² and an Fill Factor of ~ 84%. This leads to a theoretical conversion efficiency of 27.5% (monolithic) to 29% (tandem), which is much higher than the theoretical final conversion efficiency of ~ 24.5% achieved by Passivated Emitter and Rear Cell and Passivated Emitter and Rear Locally-diffused solar cells at a short-circuit voltage of 706 mV. To further approach the theoretical maximum efficiency, improvements, and optimization of the fabrication process, as well as change in material of the front emitter layer and thus the band gap, conductivity, and defect density can be adopted. Efficiencies of up to 28.27% were achieved using hydrogenated nanocrystalline silicon with a bandgap of 1.9 eV as the emitter layer.