High-efficiency nanostructured silicon solar cells on a large scale realized through the suppression of recombination channels

Process and optical modeling of black silicon

Black silicon is relevant for the photovoltaic industry when searching for low-reflectance, low-defect front surface, which is the goal of this work. We have fabricated samples using reactive ion etching (RIE) plus chemical etching for the smoothing, characterized them, and built modeling tools capable of reproducing the resulting geometric features, based on the process parameters. Reflectance is simulated using a proprietary rigorous coupled wave analysis (RCWA)-based tool, and compared with the experimental results. A good matching was achieved using a simple unit cell, and a better agreement when using a 0.5 square microns sample. Finally, an optimum trade-off between low reflectance and low thickness has been achieved.

Innovative Strategies for Photons Management on Ultrathin Silicon Solar Cells

Silicon (Si), the eighth most common element in the known universe by mass and widely applied in the industry of electronics chips and solar cells, rarely emerges as a pure element in the Earth's crust. Optimizing its manufacturing can be crucial in the global challenge of reducing the cost of renewable energy modules and implementing sustainable development goals in the future. In the industry of solar cells, this challenge is stimulating studies of ultrathin Si-based architectures, which are rapidly attracting broad attention. Ultrathin solar cells require up to two orders of magnitude less Si than conventional solar cells, and owning to a flexible nature, they are opening applications in different industries that conventional cells do not yet serve. Despite these attractive factors, a difficulty in ultrathin Si solar cells is overcoming the weak light absorption at near-infrared wavelengths. The primary goal in addressing this problem is scaling up cost-effective and innovative textures for anti-reflection and light-trapping with shallower depth junctions, which can offer similar performances to traditional thick modules. This review provides an overview of this area of research, discussing this field both as science and engineering and highlighting present progress and future outlooks.

Multi-Carrier Generation in Organic-Passivated Black Silicon Solar Cells with Industrially Feasible Processes

The innate inverse Auger effect within bulk silicon can result in multiple carrier generation. Observation of this effect is reliant upon low high-energy photon reflectance and high-quality surface passivation. In the photovoltaics industry, metal-assisted chemical etching (MACE) to afford black silicon (b-Si) can provide a low high-energy photon reflectance. However, an industrially feasible and cheaper technology to conformally passivate the outer-shell defects of these nanowires is currently lacking. Here, a technology is introduced to infiltrate black silicon nanopores with a simple and vacuum-free organic passivation layer that affords millisecond-level minority carrier lifetimes and matches perfectly with existing solution-based processing of the MACE black silicon. Advancements such as the demonstration of an excellent passivation effect whilst also being low reflectance provide a new technological route for inverse Auger multiple carrier generation and an industrially feasible technical scheme for the development of the MACE b-Si solar cells.

Graphene Metamaterial 3D Conformal Coating for Enhanced Light Harvesting

Silicon (Si) photovoltaic devices present possible avenues for overcoming global energy and environmental challenges. The high reflection and surface recombination losses caused by the Si interface and its nanofabrication process are the main hurdles for pursuing a high energy conversion efficiency. However, recent advances have demonstrated great success in improving device performance via proper Si interface modification with the optical and electrical features of two-dimensional (2D) materials. Firmly integrating large-area 2D materials with 3D Si nanostructures with no gap in between, which is essential for optimizing device performance, has rarely been achieved by any technique due to the complex 3D morphology of the nanostructures. Here we propose the concept of a 3D conformal coating of graphene metamaterials, in which the 2D graphene layers perfectly adapt to the 3D Si curvatures, leading to a universal 20% optical reflection decrease and a 60% surface passivation improvement. In a further application of this metamaterial 3D conformal coating methodology to standard Si solar cells, an overall 23% enhancement of the solar energy conversion efficiency is achieved. The 3D conformal coating strategy could be readily extended to various optoelectronic and semiconductor device systems with peculiar performance, offering a pathway for highly efficient energy-harvesting and storage solutions.

Bioinspired Compound Eyes for Diffused Light-Harvesting Application

Natural compound eyes endow arthropods with wide-field high-performance light-harvesting capability that enables them to capture prey and avoid natural enemies in dim light. Inspired by natural compound eyes, a curved artificial-compound-eye (cACE) photodetector for diffused light harvesting is proposed and fabricated, and its light-harvesting capability is systematically investigated. The cACE photodetector is fabricated by introducing a cACE as a light-harvesting layer on the surface of a silicon-based photodetector, with the cACE being prepared via planar artificial-compound-eye (pACE) template deformation. The distinctive geometric morphology of the as-prepared cACE effectively reduces its surface reflection and the dependence of the projected area on the incident light direction, thereby significantly improving the light-harvesting ability and output photocurrent of the silicon-based photodetector. Furthermore, the performances of cACE, pACE, and bare polydimethylsiloxane (PDMS)-attached photodetectors as diffused light detectors are investigated under different luminances. The cACE-photodetector output photocurrent is 1.395 and 1.29 times those of the bare PDMS-attached and pACE photodetectors, respectively. Moreover, this photodetector has a desirable geometric shape. Thus, the proposed cACE photodetector will facilitate development of high-performance photodetectors for luminance sensing.

Inverted Pyramid Morphology Control by Acid Modification and Application for PERC Solar Cells

Silicon inverted pyramid (IP) structures, with lower reflectance and increased surface recombination, are one of the best choices for light-trapping structures of high-efficiency silicon solar cells. The solution process of IP generally goes through three main steps: porous silicon etched by metal-assisted chemical etching, acid etching, and alkali anisotropic etching. In this paper, the role that acid modification plays in IP preparation and the application of our optimized texture for passivated emitter and rear solar cells (PERC) were investigated. Experimental results show that acid plays a decisive role in optimizing and modifying the morphology of porous silicon; thus, the morphology of porous silicon has no direct influence on the morphology of IP. In addition, the opening size of IP is mainly determined by the size of silicon micron holes modified by the acid process. PC1D simulation results manifest that IPs can increase the short-circuit current density (J _sc) of devices by 1.04 mA/cm² and power conversion efficiency by 0.55%; hence, our optimized IP-based PERC achieve the highest simulative conversion efficiency of 23.21%. This is an effective and important way to manipulate the structure of IP, which points out the direction of fabrication and application of high-efficiency IP textures.

Effect of morphology on the photoelectrochemical performance of nanostructured Cu2O photocathodes

Cu₂O is a promising earth-abundant semiconductor photocathode for sunlight-driven water splitting. Characterization results are presented to show how the photocurrent density (J_ph), onset potential (E_onset), band edges, carrier density (N_A), and interfacial charge transfer resistance (R_ct) are affected by the morphology and method used to deposit Cu₂O on a copper foil. Mesoscopic and planar morphologies exhibit large differences in the values ofN_AandR_ct. However, these differences are not observed to translate to other photocatalytic properties of Cu₂O. Mesoscopic and planar morphologies exhibit similar bandgap (e.g.) and flat band potential (E_fb) values of 1.93 ± 0.04 eV and 0.48 ± 0.06 eV respectively.E_onsetof 0.48 ± 0.04 eV obtained for these systems is close to theE_fbindicating negligible water reduction overpotential. Electrochemically deposited planar Cu₂O provides the highest photocurrent density of 5.0 mA cm^-2at 0 V vs reversible hydrogen electrode (RHE) of all the morphologies studied. The photocurrent densities observed in this study are among the highest reported values for bare Cu₂O photocathodes.

Broad-Band Ultra-Low-Reflectivity Multiscale Micro-Nano Structures by the Combination of Femtosecond Laser Ablation and In Situ Deposition

Functional surfaces with broad-band ultralow optical reflection have many potential applications in areas like national defense and energy conversion. For efficient, high-quality manufacturing of material surfaces with antireflection features, a novel machining method for multiscale micro-nano structures is proposed. This method can enable the collaborative manufacturing of both microstructures via laser ablation and micro-nano structures with high porosity via in situ deposition, and it can simplify the fabrication process of multiscale micro-nano structures. As a result, substantially improved antireflection properties of the treated material surface can be realized by optimizing light trapping of the microstructures and enhancing the effective medium effect for the micro-nano structures with high porosity. In ultraviolet-visible-near-infrared regions, average reflectances, as low as 2.21 and 3.33%, are achieved for Si and Cu surfaces, respectively. Furthermore, the antireflection effect of the treated surface can also be extended to the mid-infrared wavelength range, where the average reflectances for the Si and Cu surfaces decrease to 5.28 and 5.18%, respectively. This novel collaborative manufacturing method is both simple and adaptable for different materials, which opens new doors for the preparation of broad-band ultra-low-reflectivity materials.

High-Performance Free-Standing Flexible Photodetectors Based on Sulfur-Hyperdoped Ultrathin Silicon

Flexible photodetectors (PDs) prepared with silicon-based materials have received considerable attention for their use in a wide range of portable and wearable applications. In this study, we present the first free-standing flexible PD based on sulfur-hyperdoped ultrathin silicon, which was fabricated using a femtosecond laser in a SF₆ atmosphere. It is found that the fabricated device exhibits excellent performance of broadband photoresponse from 400 to 1200 nm, with a peak responsivity of 63.79 A/W @ 870 nm at a low bias voltage of -2 V, corresponding to an external quantum efficiency reaching 9092%, which surpasses most values reported for silicon-based flexible PDs. In addition, the device shows a fast response speed (rise time τ_r = 68 μs) and stable detection performance with good mechanical flexibility. The high-performance PD described here suggests a promising way in flexible applications for sensors, imaging systems, and optical communication systems.

Influence of Defects on Excited-State Dynamics in Lead Halide Perovskites: Time-Domain ab Initio Studies

This Perspective summarizes recent research into the excited-state dynamics in lead halide perovskites that are of paramount importance for photovoltaic and photocatalytic applications. Nonadiabatic molecular dynamics combined with time-domain ab initio density functional theory allows one to mimic time-resolved spectroscopy experiments at the atomistic level of detail. The focus is placed on realistic aspects of perovskite materials, including point defects, surfaces, grain boundaries, mixed stoichiometries, dopants, and interfaces. The atomistic description of the quantum dynamics of electron and hole trapping and recombination, provided by the time-domain ab initio simulations, generates important insights into the mechanisms of charge and energy losses and guides the development of high-performance perovskite solar cell devices.

Single-crystal silicon-based electrodes for unbiased solar water splitting: current status and prospects

This review describes recent developments of single-crystal silicon (Si) as the photoelectrode material for solar water splitting, including the promising strategies to obtain highly efficient and stable single-crystal Si-based photoelectrodes for hydrogen evolution and water oxidation, as well as the future development of spontaneous solar water splitting with single-crystal Si-based tandem cells.

Antireflective Paraboloidal Microlens Film for Boosting Power Conversion Efficiency of Solar Cells

Microlens arrays can improve light transmittance in optical devices or enhance the photoelectrical conversion efficiency of photovoltaic devices. Their surface morphology (aspect ratio and packed density) is vital to photon management in solar cells. Here, we report a 100% packed density paraboloidal microlens array (PMLA), with a large aspect ratio, fabricated by direct-write UV laser photolithography coupled with soft imprint lithography. Optical characterization shows that the PMLA structure can remarkably decrease the front-side reflectance of solar cell device. The measured electrical parameters of the solar cell device clearly and consistently demonstrate that the PMLA film can considerably improve the photoelectrical conversion efficiency. In addition, the PMLA film has superhydrophobic properties, verified by measurement of a large water contact angle, and can enhance the self-cleaning capability of solar cell devices.

High sensitive position-dependent photodetection observed in Cu-covered Si nanopyramids

Silicon nanopyramids with the excellent ability of light absorption have been mostly reported in solar cells. Here, we report an obviously enhanced lateral photovoltaic effect (LPE) in copper-nanoparticle-covered random Si nanopyramids (Cu@Si-pyramid). Remarkable photoelectric responses are achieved in broadband from 405 to 780 nm. Furthermore, a prominent LPE is double-enhanced from 74.0 to 157.9 mV mm^-1 when the linear region decreases from 3 to 1 mm. Finite-difference time-domain simulation is applied to investigate the origin of the exceptional results. This work declares a position-sensitive property of Si-nanopyramid systems and proposes promising applications to photodetections based on LPE.

Fabrication of 20.19% Efficient Single-Crystalline Silicon Solar Cell with Inverted Pyramid Microstructure

This paper reports inverted pyramid microstructure-based single-crystalline silicon (sc-Si) solar cell with a conversion efficiency up to 20.19% in standard size of 156.75 × 156.75 mm². The inverted pyramid microstructures were fabricated jointly by metal-assisted chemical etching process (MACE) with ultra-low concentration of silver ions and optimized alkaline anisotropic texturing process. And the inverted pyramid sizes were controlled by changing the parameters in both MACE and alkaline anisotropic texturing. Regarding passivation efficiency, the textured sc-Si with normal reflectivity of 9.2% and inverted pyramid size of 1 μm was used to fabricate solar cells. The best batch of solar cells showed a 0.19% higher of conversion efficiency and a 0.22 mA cm^-2 improvement in short-circuit current density, and the excellent photoelectric property surpasses that of the same structure solar cell reported before. This technology shows great potential to be an alternative for large-scale production of high efficient sc-Si solar cells in the future.

Controllable nanoscale inverted pyramids for highly efficient quasi-omnidirectional crystalline silicon solar cells

Nanoscale inverted pyramid structures (NIPs) have always been regarded as one of the paramount light management schemes to achieve extraordinary performance in various devices, especially in solar cells, due to their outstanding antireflection ability with relative lower surface enhancement ratio. However, current approaches to fabricating NIPs are complicated and not cost-effective for massive cell production in the photovoltaic industry. Here, controllable NIPs are fabricated on crystalline silicon (c-Si) wafers by Ag-catalyzed chemical etching and alkaline modification, which is a preferable all-solution-processed method. Through applying the NIPs to c-Si solar cells and optimizing the cell design, we have successfully achieved highly efficient textured solar cells with NIPs of a champion efficiency of 20.5%. Significantly, these NIPs are further demonstrated to possess a quasi-omnidirectional property over broad sunlight incident angles of approximately 0°-60°. Moreover, NIPs are theoretically revealed to offer light trapping advantages for ultrathin c-Si solar cells. Hence, NIPs formed by a controllable method exhibit great potential to be used in the future photovoltaic industry as surface texture.

Contact Selectivity Engineering in a 2 μm Thick Ultrathin c-Si Solar Cell Using Transition-Metal Oxides Achieving an Efficiency of 10.8

In this paper, the integration of metal oxides as carrier-selective contacts for ultrathin crystalline silicon (c-Si) solar cells is demonstrated which results in an ∼13% relative improvement in efficiency. The improvement in efficiency originates from the suppression of the contact recombination current due to the band offset asymmetry of these oxides with Si. First, an ultrathin c-Si solar cell having a total thickness of 2 μm is shown to have >10% efficiency without any light-trapping scheme. This is achieved by the integration of nickel oxide (NiO_x) as a hole-selective contact interlayer material, which has a low valence band offset and high conduction band offset with Si. Second, we show a champion cell efficiency of 10.8% with the additional integration of titanium oxide (TiO_x), a well-known material for an electron-selective contact interlayer. Key parameters including V_oc and J_sc also show different degrees of enhancement if single (NiO_x only) or double (both NiO_x and TiO_x) carrier-selective contacts are integrated. The fabrication process for TiO_x and NiO_x layer integration is scalable and shows good compatibility with the device.

Optimization of the Surface Structure on Black Silicon for Surface Passivation

Black silicon shows excellent anti-reflection and thus is extremely useful for photovoltaic applications. However, its high surface recombination velocity limits the efficiency of solar cells. In this paper, the effective minority carrier lifetime of black silicon is improved by optimizing metal-catalyzed chemical etching (MCCE) method, using an Al₂O₃ thin film deposited by atomic layer deposition (ALD) as a passivation layer. Using the spray method to eliminate the impact on the rear side, single-side black silicon was obtained on n-type solar grade silicon wafers. Post-etch treatment with NH₄OH/H₂O₂/H₂O mixed solution not only smoothes the surface but also increases the effective minority lifetime from 161 μs of as-prepared wafer to 333 μs after cleaning. Moreover, adding illumination during the etching process results in an improvement in both the numerical value and the uniformity of the effective minority carrier lifetime.

Realization of Quasi-Omnidirectional Solar Cells with Superior Electrical Performance by All-Solution-Processed Si Nanopyramids

Large-scale (156 mm × 156 mm) quasi-omnidirectional solar cells are successfully realized and featured by keeping high cell performance over broad incident angles (θ), via employing Si nanopyramids (SiNPs) as surface texture. SiNPs are produced by the proposed metal-assisted alkaline etching method, which is an all-solution-processed method and highly simple together with cost-effective. Interestingly, compared to the conventional Si micropyramids (SiMPs)-textured solar cells, the SiNPs-textured solar cells possess lower carrier recombination and thus superior electrical performances, showing notable distinctions from other Si nanostructures-textured solar cells. Furthermore, SiNPs-textured solar cells have very little drop of quantum efficiency with increasing θ, demonstrating the quasi-omnidirectional characteristic. As an overall result, both the SiNPs-textured homojunction and heterojunction solar cells possess higher daily electric energy production with a maximum relative enhancement approaching 2.5%, when compared to their SiMPs-textured counterparts. The quasi-omnidirectional solar cell opens a new opportunity for photovoltaics to produce more electric energy with a low cost.

Localized Surface Plasmon Induced Position-Sensitive Photodetection in Silicon-Nanowire-Modified Ag/Si

Surface plasmon-based approaches are widely applied to improve the efficiency of photoelectric devices such as photosensors and photocells. In order to promote the light absorption and electron-hole pair generation in devices, metallodielectric nanostructures are used to boost the growth of surface plasmons. Here, silicon nanowires (SiNWs) are used to modify a metal-semiconductor structure; thus, Ag/SiNWs/Si is manufactured. In this system, a large increased lateral photovoltaic effect (LPE) is detected with a maximum positional sensitivity of 65.35 mV mm^-1 , which is ≈53-fold and 1000-fold compared to the conventional Ag/Si (1.24 mV mm^-1 ) and SiNWs/Si (0.06 mV mm^-1 ), respectively. It is demonstrated that localized surface plasmons (LSPs) contribute a lot to the increment of LPE. Furthermore, through the surface-enhanced Raman scattering spectra of rhodamine-6G and finite-difference time-domain simulation, it is illustrated that silver-coated SiNWs support strong LSPs. The results propose an enhancement mechanism based on LSPs to facilitate the photoelectric conversion in LPE and offer an effective way to improve the sensitivity of photodetectors.

Nanostructured Silicon Used for Flexible and Mobile Electricity Generation

The use of nanostructured silicon for the generation of electricity in flexible and mobile devices is reviewed. This field has attracted widespread interest in recent years due to the emergence of plastic electronics. Such developments are likely to alter the nature of power sources in the near future. For example, flexible photovoltaic cells can supply electricity to rugged and collapsible electronics, biomedical devices, and conformable solar panels that are integrated with the curved surfaces of vehicles or buildings. Here, the unique optical and electrical properties of nanostructured silicon are examined, with regard to how they can be exploited in flexible photovoltaics, thermoelectric generators, and piezoelectric devices, which serve as power generators. Particular emphasis is placed on organic-silicon heterojunction photovoltaic devices, silicon-nanowire-based thermoelectric generators, and core-shell silicon/silicon oxide nanowire-based piezoelectric devices, because they are flexible, lightweight, and portable.

Designing nanobowl arrays of mesoporous TiO₂ as an alternative electron transporting layer for carbon cathode-based perovskite solar cells

In this work, we have designed a mesoporous TiO2 nanobowl (NB) array with pore size, bowl size and film thickness being easily controllable by the sol-gel process and the polystyrene (PS) template diameter. Based on the TiO2 NB array, we fabricated carbon cathode based perovskite solar cells (C-PSCs) to investigate the impact of TiO2 NB nanostructures on the performance of the as-obtained C-PSCs devices. As expected, the TiO2 NB based devices show a higher power conversion efficiency (PCE) than that of the planar counterpart, mainly due to the enhanced light absorption arising from the NB-assisted light management, the improved pore-filling of high quality perovskite crystals and the increased interface contact for rapid electron extraction and fast charge transport. Leveraging these advantages of the novel TiO2 NB film, the 220 nm-PS templated TiO2 NB based devices performed the best on both light absorption capability and charge extraction, and achieved a PCE up to 12.02% with good stability, which is 37% higher than that of the planar counterpart. These results point to a viable and convenient route toward the fabrication of TiO2 ETL nanostructures for high performance PSCs.

Low-Pressure-Assisted Coating Method To Improve Interface between PEDOT:PSS and Silicon Nanotips for High-Efficiency Organic/Inorganic Hybrid Solar Cells via Solution Process

Nanostructured silicon hybrid solar cells are promising candidates for a new generation photovoltaics because of their light-trapping abilities and solution processes. However, the performance of hybrid organic/Si nanostructure solar cells is hindered because of carrier recombination at surface and poor coverage of organic material poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (

PEDOT

PSS) on nanostructures. Here we demonstrate low-pressure-assisted coating method of

PEDOT

PSS on surface-modified silicon nanotips with broadband light-trapping characteristics to improve interface property and to achieve high-efficiency hybrid solar cells through a solution process. The approach enhances the effective minority-carrier lifetime and the coverage of

PEDOT

PSS on the surface of nanostructures. Hybrid solar cells fabricated with surface-modified nanotips exhibit a high fill factor of 70.94%, short-circuit current density of 35.36 mA/cm(2), open-circuit voltage of 0.528 V, and power conversion efficiency of 13.36%. The high efficiency and the high fill factor are achieved because of conformal coating of

PEDOT

PSS via a low-pressure-assisted coating process, excellent light harvesting without sacrificing the minority-carrier lifetime, and efficient charge separation/collection of photogenerated carriers.

Varying Surface Chemistries for p-Doped and n-Doped Silicon Nanocrystals and Impact on Photovoltaic Devices

Doping of quantum confined nanocrystals offers unique opportunities to control the bandgap and the Fermi energy level. In this contribution, boron-doped (p-doped) and phosphorus-doped (n-doped) quantum confined silicon nanocrystals (SiNCs) are surface-engineered in ethanol by an atmospheric pressure radio frequency microplasma. We reveal that surface chemistries induced on the nanocrystals strongly depend on the type of dopants and result in considerable diverse optoelectronic properties (e.g., photoluminescence quantum yield is enhanced more than 6 times for n-type SiNCs). Changes in the position of the SiNCs Fermi levels are also studied and implications for photovoltaic application are discussed.

Enhanced photovoltaic performance of inverted pyramid-based nanostructured black-silicon solar cells passivated by an atomic-layer-deposited Al2O3 layer

Inverted pyramid-based nanostructured black-silicon (BS) solar cells with an Al2O3 passivation layer grown by atomic layer deposition (ALD) have been demonstrated. A multi-scale textured BS surface combining silicon nanowires (SiNWs) and inverted pyramids was obtained for the first time by lithography and metal catalyzed wet etching. The reflectance of the as-prepared BS surface was about 2% lower than that of the more commonly reported upright pyramid-based SiNW BS surface over the whole of the visible light spectrum, which led to a 1.7 mA cm(-2) increase in short circuit current density. Moreover, the as-prepared solar cells were further passivated by an ALD-Al2O3 layer. The effect of annealing temperature on the photovoltaic performance of the solar cells was investigated. It was found that the values of all solar cell parameters including short circuit current, open circuit voltage, and fill factor exhibit a further increase under an optimized annealing temperature. Minority carrier lifetime measurements indicate that the enhanced cell performance is due to the improved passivation quality of the Al2O3 layer after thermal annealing treatments. By combining these two refinements, the optimized SiNW BS solar cells achieved a maximum conversion efficiency enhancement of 7.6% compared to the cells with an upright pyramid-based SiNWs surface and conventional SiNx passivation.

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

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.

Superior broadband antireflection from buried Mie resonator arrays for high-efficiency photovoltaics

Establishing reliable and efficient antireflection structures is of crucial importance for realizing high-performance optoelectronic devices such as solar cells. In this study, we provide a design guideline for buried Mie resonator arrays, which is composed of silicon nanostructures atop a silicon substrate and buried by a dielectric film, to attain a superior antireflection effect over a broadband spectral range by gaining entirely new discoveries of their antireflection behaviors. We find that the buried Mie resonator arrays mainly play a role as a transparent antireflection structure and their antireflection effect is insensitive to the nanostructure height when higher than 150 nm, which are of prominent significance for photovoltaic applications in the reduction of photoexcited carrier recombination. We further optimally combine the buried Mie resonator arrays with micron-scale textures to maximize the utilization of photons, and thus have successfully achieved an independently certified efficiency of 18.47% for the nanostructured silicon solar cells on a large-size wafer (156 mm × 156 mm).