Effective optimization of emitters and surface passivation for nanostructured silicon solar cells

Li, Ping; Wei, Yi; Tan, Xin; Li, Xiaoxuan; Wang, Yuxuan; Zhao, Zengchao; Yuan, Ze; Liu, Aimin

doi:10.1039/c6ra20945a

Cited by 18 publications

(23 citation statements)

References 41 publications

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“…However, there are challenges with integrating B-Si into solar cells including increased surface recombination associated with its increased surface area and the increased Auger recombination associated with its enhanced doping effect [15]. Studies of doped B-Si typically focus on recombination mitigation strategies, including additional texture modifications [15]- [17], advanced passivation techniques [18]- [20], modified diffusion processes [18], [21] or a transition to larger micron-scale features [13]. As such, only cursory explanations of the enhanced doping are typically provided.…”

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confidence: 99%

On the Enhanced Phosphorus Doping of Nanotextured Black Silicon

Scardera

Wang

Khan

et al. 2021

IEEE J. Photovoltaics

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The integration of nanotextured black silicon (B-Si) into solar cells is often complicated by its enhanced phosphorus doping effect, which is typically attributed to increased surface area. In this article, we show that B-Si's surface-to-volume ratio, or specific surface area (SSA), which is directly related to surface reactivity, is a better indicator of reduced sheet resistance. We investigate six B-Si conditions with varying dimensions based on two morphology types prepared using metal-catalyzed chemical etching and reactive-ion etching. We demonstrate that for a POCl 3 diffusion, B-Si sheet resistance decreases with increasing SSA, regardless of surface area. 2-D dopant contrast imaging of different textures with similar surface areas also indicates that the extent of doping is enhanced with increasing SSA. 3-D diffusion simulations of nanocones show that both the extent of radial doping within a texture feature and the metallurgical junction depth in the underlying substrate increase with increasing SSA. We suggest SSA should be considered more readily when studying B-Si and its integration into solar cells. Index Terms-Black silicon, phosphorus doping, silicon nanotexture, surface area, surface-to-volume ratio. I. INTRODUCTIONN ANOTEXTURED silicon often falls under the collective label of black silicon (B-Si) which typically describes surfaces with low reflectance across a wide wavelength range (ultraviolet to near-infrared) and which appear black to the eye. B-Si can be prepared using a myriad of techniques and covers a wide range of surface morphologies and feature dimensions (from nano to micron-scale), including nanoporous layers [1],

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confidence: 99%

On the Enhanced Phosphorus Doping of Nanotextured Black Silicon

Scardera

Wang

Khan

et al. 2021

IEEE J. Photovoltaics

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“…14 Recently, stacks of thermally grown SiO 2 and PE-CVD SiNx films have been explored as a passivation scheme for highly n-type-doped black Si surfaces. 15,16 Interestingly, ALD SiO 2 /Al 2 O 3 stacks have also emerged as an alternative passivation scheme for n þ Si. 17 The ALD SiO 2 /Al 2 O 3 stacks do not exhibit a high negative Q f , as a sufficiently thick SiO 2 layer prevents the injection of electrons from the c-Si bulk into the Al 2 O 3 .…”

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confidence: 99%

Surface passivation of n-type doped black silicon by atomic-layer-deposited SiO2/Al2O3 stacks

Loo

Ingenito

Verheijen

et al. 2017

Applied Physics Letters

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Black silicon (b-Si) nanotextures can significantly enhance the light absorption of crystalline silicon solar cells. Nevertheless, for a successful application of b-Si textures in industrially relevant solar cell architectures, it is imperative that charge-carrier recombination at particularly highly n-type doped black Si surfaces is further suppressed. In this work, this issue is addressed through systematically studying lowly and highly doped b-Si surfaces, which are passivated by atomic-layer-deposited Al2O3 films or SiO2/Al2O3 stacks. In lowly doped b-Si textures, a very low surface recombination prefactor of 16 fA/cm2 was found after surface passivation by Al2O3. The excellent passivation was achieved after a dedicated wet-chemical treatment prior to surface passivation, which removed structural defects which resided below the b-Si surface. On highly n-type doped b-Si, the SiO2/Al2O3 stacks result in a considerable improvement in surface passivation compared to the Al2O3 single layers. The atomic-layer-deposited SiO2/Al2O3 stacks therefore provide a low-temperature, industrially viable passivation method, enabling the application of highly n- type doped b-Si nanotextures in industrial silicon solar cells.

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“…The surface electrodes should have a negative impact due to the surface wave coupling to the emitter and losses in metallic materials, while the conductive substrate normally improves the efficiency by limiting long-wavelength radiative transfer as a back-reflector 10 , 11 . Also, the nano patterning of the PV cells is likely to increase the electrical losses via surface recombination 31 but this effect is difficult to predict due to the complexity of determining the spatial generation and recombination of EHPs in this scenario, so this effect is outside the scope of this analysis. For practical applications, methods such as surface passivation 32 may be used to reduce the electrical losses for deeply etched group III–V semiconductors.…”

Section: Discussionmentioning

confidence: 99%

Simple Rectangular Gratings as a Near-Field “Anti-Reflection” Pattern for GaSb TPV Cells

Liu

Yang

et al. 2017

Sci Rep

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We show theoretically that 2D rectangular gratings on the surface of GaSb can serve as an “anti-reflection” pattern for nano-gap thermophotovoltaic (TPV) devices, which significantly enhances near-field radiative flux from the emitter to a GaSb cell, thus improving output power and conversion efficiency. The system in this study is a 200-nm gap TPV power generation system with a planar infrared plasmonic emitter and GaSb cell. Rigorous coupled-wave analysis is used to calculate the spectral near-field radiative flux involving periodic structures. The simulation shows that when coupled with a near-infrared plasmonic bulk emitter, adding gratings on the GaSb cell surface results in strong spectral enhancement above the cell’s bandgap and suppression for low-energy photon transmission, an effect that cannot be fully predicted by the effective medium theory. The resultant peak spectral heat flux is 2.8 times as high as the case without surface structures and the radiative transfer efficiency increased to 24.8% from the original 14.5% with the emitter temperature at 1800 K. The influence of the grating’s geometry parameters on the enhancement and peak frequency is further discussed with rigorous calculation of the spatial distribution of thermal radiative transfer that provided insight into the physical mechanism.

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Effective optimization of emitters and surface passivation for nanostructured silicon solar cells

Abstract: High efficiency black silicon solar cells achieved by optimization of emitter and surface passivation.

Cited by 18 publications

References 41 publications

On the Enhanced Phosphorus Doping of Nanotextured Black Silicon

On the Enhanced Phosphorus Doping of Nanotextured Black Silicon

Surface passivation of n-type doped black silicon by atomic-layer-deposited SiO2/Al2O3 stacks

Simple Rectangular Gratings as a Near-Field “Anti-Reflection” Pattern for GaSb TPV Cells

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