Characterization and modeling of low temperature surface passivation for interdigitated back contact silicon hetero-junction solar cell

Low process temperature (<;300°C) surface passivation has been proposed for interdigitated back contact silicon hetero-junction (IBC-SHJ) solar cell. A quantitative knowledge of the interface properties of various passivation structures is essential to understand the device physics of IBC-SHJ solar cells, and thus to guide device design and process optimization. In this work, surface passivation of n-type crystalline silicon (c-Si) using the stack structure which consists of an intrinsic amorphous silicon (a-Si) layer capped by a silicon nitride (a-SiN_x) layer or by a doped a-Si layer was investigated. A positive fixed charge of ~10¹¹cm^-2 was measured in a-SiN_x film from high frequency capacitance-voltage characteristics of the metal-insulator-semiconductor device. Surface recombination velocity (SRV) measured as a function of injection level, was modeled to extract the interface properties via extended Shockley-Read-Hall (SRH) formalism. The model analysis indicates that mid-gap interface defect levels range from 4.4×10¹⁰cm^-2eV^-1 to 2.4×10¹¹cm^-2eV^-1 in the IBC-SHJ solar cell. 2D simulation of the IBC-SHJ solar cell further confirms the characterization and modeling of the interfaces developed in this work.