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This paper investigates effects of silver nanoparticles (Ag NPs) layer thickness towards properties of black silicon (b-Si) fabricated by two-step metal-assisted chemical etching for potential application in photovoltaic (PV) devices. Ag NPs with different layer thicknesses (1.3-5.1 µm) are deposited on monocrystalline silicon (mono c-Si) wafers by electroless chemical deposition in AgNO 3 /HF aqueous solution for 10-40 s. This is followed by etching in HF:H 2 O 2 :DI H 2 O aqueous solution for 20 s. Surface morphological investigation confirms presence of b-Si nanowires with height of 250-577 nm and diameter of 100-200 nm. The b-Si nanowires suppress broadband reflectance from the wafers over 300-1100 nm wavelength region, due to refractive index grading effect. Sample with Ag NPs layer thickness of 5.1 µm exhibits b-Si nanowires with average height of 577 nm and average diameter of 200 nm after etching. This sample demonstrates the lowest weighted average reflectance of 5.5% compared to other samples. This sample exhibits absorption of 96.5% at wavelength of 600 nm. The enhanced broadband light absorption leads to maximum potential short-circuit current density (J sc(max)) of 39.7 mA/cm 2 , or 51% relative enhancement compared to planar reference sample.

This paper reports broadband anti-reflection in black silicon (b-Si) fabricated by two-step metal-assisted chemical etching (MACE) for potential photovoltaic (PV) applications. The method involves deposition of silver nanoparticles (Ag NPs) in aqueous solution of HF:AgNO3, followed by etching in HF:H2O2:DI H2O solution for different duration (10-25 s). Effects of etching time towards surface morphological and optical properties of b-Si nanowires are investigated. Surface morphological characterization confirms presence of b-Si nanowires with heights of 350-570 nm and diameter of 150-300 nm. The b-Si nanowires exhibit outstanding broadband anti-reflection due to refractive index grading effect. This is represented as weighted average reflection (WAR) in the 300-1100 nm wavelength region. After 20 s of etching, b-Si nanowires with height of 570 nm and width of about 200 nm are produced. The nanowires demonstrate WAR of 5.5%, which represents the lowest WAR in this investigation. This results in absorption of 95.6% at wavelength of 600 nm. The enhanced broadband light absorption yields maximum potential short-circuit current density (Jsc(max)) of up to 39.7 mA/cm2, or 51% enhancement compared to c-Si reference. This facile b-Si fabrication method for broadband enhanced anti-reflection could be a promising technique to produce potential PV devices with high photocurrent.

Purpose This paper aims to present investigation on textured polyimide (PI) substrate for enhanced light absorption in flexible black silicon (bSi). Design/methodology/approach Flexible bSi with thickness of 60 µm is used in this work. To texture the PI substrate, copper-seeding technique is used. A copper (Cu) layer with a thickness of 100 nm is deposited on PI substrate by sputtering. The substrate is then annealed at 400°C in air ambient for different durations of 60, 90 and 120 min. Findings With 90 min of annealing, root mean square roughness as large as 130 nm, peak angle of 24° and angle distribution of up to 87° are obtained. With this texturing condition, the flexible bSi exhibits maximum potential short-circuit current density (Jmax) of 40.33 mA/cm2, or 0.45 mA/cm2 higher compared to the flexible bSi on planar PI. The improvement is attributed to enhanced light scattering at the flexible bSi/textured PI interface. The findings from this work demonstrate that the optimization of the PI texturing via Cu-seeding process leads to an enhancement in the long wavelengths light absorption and potential Jmax in the flexible bSi absorber. Originality/value Demonstrated enhanced light absorption and potential Jmax in flexible bSi on textured PI substrate (compared to planar PI substrate) by Cu-seeding with different annealing durations.