Efficiency Enhancement of Nanotextured Black Silicon Solar Cells Using Al₂O₃/TiO₂ Dual-Layer Passivation Stack Prepared by Atomic Layer Deposition

Abstract

In this study, efficient nanotextured black silicon (NBSi) solar cells composed of silicon nanowire arrays and an Al2O3/TiO2 dual-layer passivation stack on the n(+) emitter were fabricated. The highly conformal Al2O3 and TiO2 surface passivation layers were deposited on the high-aspect-ratio surface of the NBSi wafers using atomic layer deposition. Instead of the single Al2O3 passivation layer with a negative oxide charge density, the Al2O3/TiO2 dual-layer passivation stack treated with forming gas annealing provides a high positive oxide charge density and a low interfacial state density, which are essential for the effective field-effect and chemical passivation of the n(+) emitter. In addition, the Al2O3/TiO2 dual-layer passivation stack suppresses the total reflectance over a broad range of wavelengths (400-1000 nm). Therefore, with the Al2O3/TiO2 dual-layer passivation stack, the short-circuit current density and efficiency of the NBSi solar cell were increased by 11% and 20%, respectively. In conclusion, a high efficiency of 18.5% was achieved with the NBSi solar cells by using the n(+)-emitter/p-base structure passivated with the Al2O3/TiO2 stack.

Recombination processes in passivated boron-implanted black silicon emitters

“…1 While surface recombination has limited bSi electrical performance for years, advances in passivation-and especially the use of atomic layer deposition (ALD)-have made it possible to obtain low surface recombination velocities in such high aspect ratio surfaces. [2][3][4][5] Consequently, research on bSi emitters has been steadily expanding in the past few years, [6][7][8][9][10] and ALD has also demonstrated effective passivation of both phosphorus 11 and boron bSi emitters. 12,13 However, most of the research involving textured emitters has been limited to emitter doping via diffusion, although a number of studies point out the necessity of a compromise in the bSi dimensions in order to limit emitter recombination.…”

Dual Management of Electrons and Photons to Get High‐Performance Light Emitting Devices Based on Si Nanowires and Si Quantum Dots with Al2O3‐Ag Hybrid Nanostructures

“…In addition, Al/p‐type Si NW/Al 2 O 3 /Al metal–oxide–semiconductor (MOS) capacitors are also fabricated to quantificationally evaluate the passivation effect of thermal ALD Al 2 O 3 . The equivalent fixed charge ( Q ox ) and surface defect state density ( D it ) values of Al 2 O 3 are deduced through measuring capacitance–voltage ( C – V ) and conductivity–voltage ( G – V ) curves in a frequency range from 10 kHz to 1 MHz with the conductance method (see the Supporting Information). The equivalent fixed charge is negative and the Q ox / q value is calculated as 1.53 × 10 13 cm −2 , implying that thermal ALD Al 2 O 3 indeed has the field‐effect passivation to p‐type Si NWs .…”

Non-Vacuum Process for Production of Crystalline Silicon Solar Cells

“…(1) which is above these values. In some references, also, the advantage of double-layer ARC was shown with low reflectance less than single layer ARC [25][26][27][28]. Moreover, another advantage of TiO 2 /Al 2 O 3 is the non-vacuum spray pyrolysis deposition, which can realize the lower cost production system than batch vacuum process like a SiN x in terms of installation and running costs [29].…”