High efficiency TOPCon solar cells with micron/nano-structured emitter for a balance of light-trapping and surface passivation

At present, conventional micron-pyramid texture is imperfect for further reducing optical reflection loss and improving photoelectric conversion efficiency (PCE) of tunnel oxide passivating contact (TOPCon) solar cells. Herein, reactive ion etching technique is used to fabricate nanopores on top of pre-formed micron-pyramid silicon surface, called NPP structure. The equivalent medium layer with graded refractive index appeared on NPP textures makes the absorption of almost all incident light independent of the wavelength and angle. However, serious Auger recombination and surface recombination associated with NPP structure is detrimental to emitter passivation, usually counteracting the photocurrent gain. To identify an appropriate balance of light-trapping and surface passivation, we investigate the impact of different radio-frequency power (PRF) on the optical and electrical properties of TOPCon solar cells and discusses the underlying structural causes behind these observed improvements. Finally, we demonstrate NPP TOPCon solar cells with an average short-circuit current density of 41.44 mA/cm(2) and an average PCE of 23.55% at the PRF of 600 W. Besides, the external quantum efficiency results under various incident angles from 0 degrees to 70 degrees exhibited excellent wide-angle spectral absorption capability, which is significant for solar cells working in an outdoor environment.

Automated summary

In this study, a reactive ion etching technique is used to fabricate nanopores on top of pre-formed micron-pyramid silicon surface, called NPP structure, to improve the photoelectric conversion efficiency of TOPCon solar cells. However, the NPP structure also leads to serious Auger recombination and surface recombination, which affect the emitter passivation of the cells. By investigating the impact of different radio-frequency power on the cell's optical and electrical properties, an appropriate balance between light-trapping and surface passivation is identified.