High-efficiency black IBC c-Si solar cells with poly-Si as carrier-selective passivating contacts

Abstract

In this work, we present the application of poly-Si carrier-selective passivating contacts (CSPCs) as both polarities in interdigitated back-contacted (IBC) solar cell architectures. We compared two approaches to form a gap between the back-surface field (BSF) and emitter fingers. It is proved that the gaps prepared by both approaches are efficient in preventing carriers’ recombination. To minimize the reflection losses, we developed a novel modulated surface texturing (MST) structure as anti-reflection coating (ARC). It is obtained by superposing a nano-textured SiO₂ layer on the conventional micro-textured pyramids, which are passivated with a-Si:H / SiN_x:H layers. This approach decouples the light harvesting from the Si surface passivation, which potentially results in the highest possible optical and electrical performances of the solar cells. The reflectance (R) of the MST-ARC is very close to that of the high-aspect ratio nano-structured silicon (black-Silicon), achieving R < 1% between 450 and 1000 nm. The J₀ of MST-ARC passivated Si surface (6.3 fA/cm²) is the same as that of standard a-Si:H/SiN_x:H layers passivated pyramidally-textured Si surface. By applying this novel MST-ARC in our IBC solar cell, the highest J_SC observed in a device is 42.2 mA/cm² with a V_OC as high as 701 mV. A spectral response enhancement in case of the MST-ARC cell is observed over the whole wavelength range with respect to the cell with standard SiN_x:H ARC. The highest efficiency achieved in this work is 23.0%, with the potential to reach 24.0% in short term by using more conductive metal fingers.