Broadband light absorption enhancement in nanoporous black silicon synthesized by aluminium-catalyzed chemical etching

Abstract

Black silicon (b-Si) is an attractive light absorbing material for photovoltaic and optoelectronic applications due to its superior broadband light absorption. The b-Si is commonly synthesized using metal-catalyzed chemical etching (MCCE) process. In the recently developed aluminium-catalyzed chemical etching (ACCE) process, aluminium (Al) is being used as an effective catalyst to synthesize the nanoporous b-Si absorber. In this work, the broadband light absorption has been investigated in the nanoporous b-Si synthesized via ACCE process with varying etching duration (10–60 min). The etching of planar c-Si samples coated with 12 nm of Al film in a HF–H2O2–H2O (1-5-10 ml) solution for 30 min synthesizes the b-Si nanopores with average depth of 270.7 nm, average diameter of 41.6 nm, surface coverage of 54.7% and root mean square (RMS) roughness of 17.6 nm. With these morphological characteristics, the nanoporous b-Si demonstrates the lowest weighted average reflection (Ravg) of 9.2% and average absorption enhancement of 1.61 within 300–1100 nm spectral region. The findings from this work demonstrate the potential applications of the synthesized nanoporous b-Si absorber in photovoltaic and optoelectronic devices.