Optical losses in silicon heterojunction solar cells: analysis of record-efficiency devices and practical limits based on ray-tracing simulations

Abstract

The efficiency of record silicon heterojunction (SHJ) solar cells for both front-and-back contacted (FBC) and interdigitated back-contacted (IBC) architectures has improved significantly in recent years. This is largely due to considerable improvements in short-circuit current density (J_sc) driven by recent industrial innovations resulting in highly transparent layers and novel metallisation. In this work we present the first detailed, side-by-side J_sc loss comparison of recent record solar cells enabled by a carefully calibrated and thoroughly validated optical ray-tracing model and derive a practically achievable J_sc limit for modern FBC-SHJ and IBC-SHJ solar cells for different silicon wafer thicknesses. By modelling recent SHJ record-efficiency cells based on published data, we obtain spectrally resolved J_sc losses and estimated complex refractive indices for all functional layers used in record SHJ solar cells as of 2024 from Hanergy, Maxwell, SunDrive, LONGi, Panasonic and Kaneka. Pathways for further improvement in J_sc are also described.