Enhanced optical performance of thermochromic VO2 based on multilayer designs

VO2 is a widely studied thermochromic material for smart windows. In this work, we comprehensively studied optical responses of VO2-based multilayer structures. It is discovered that one-layer antireflection layer is capable of effectively enhancing both luminous transmittance (Tlum) and solar transmittance (Tsol), solar spectrum modulation (ΔTsol) is however quite moderate. Employing a two-top-layer strategy further improves the optical performance of VO2, especially with an increase of ΔTsol from 0.068 to 0.082. Remarkably, combining a layer with an index of 2.2 at the VO2/glass interface continues to enhance the optical performance, leading to the highest Tlum and ΔTsol among the investigated multilayer structures. Compared to the base structure of VO2/glass, it contributes to a relative enhancement of 26.4% (from 0.435 to 0.550) for Tlum (<τc), 35.3% (from 0.362 to 0.490) for Tlum (>τc), and 71.7% (from 0.060 to 0.103) for ΔTsol.

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Comparing optical performance of a wide range of perovskite/silicon tandem architectures under real-world conditions

Nanophotonics ◽

10.1515/nanoph-2020-0643 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Manvika Singh ◽

Rudi Santbergen ◽

Indra Syifai ◽

Arthur Weeber ◽

Miro Zeman ◽

...

Keyword(s):

Solar Cells ◽

Real World ◽

Solar Spectrum ◽

Photocurrent Density ◽

Angle Of Incidence ◽

Optical Study ◽

Optical Performance ◽

Tandem Solar Cells ◽

Bottom Cell ◽

Wide Range

Abstract Since single junction c-Si solar cells are reaching their practical efficiency limit. Perovskite/c-Si tandem solar cells hold the promise of achieving greater than 30% efficiencies. In this regard, optical simulations can deliver guidelines for reducing the parasitic absorption losses and increasing the photocurrent density of the tandem solar cells. In this work, an optical study of 2, 3 and 4 terminal perovskite/c-Si tandem solar cells with c-Si solar bottom cells passivated by high thermal-budget poly-Si, poly-SiOx and poly-SiCx is performed to evaluate their optical performance with respect to the conventional tandem solar cells employing silicon heterojunction bottom cells. The parasitic absorption in these carrier selective passivating contacts has been quantified. It is shown that they enable greater than 20 mA/cm2 matched implied photocurrent density in un-encapsulated 2T tandem architecture along with being compatible with high temperature production processes. For studying the performance of such tandem devices in real-world irradiance conditions and for different locations of the world, the effect of solar spectrum and angle of incidence on their optical performance is studied. Passing from mono-facial to bi-facial tandem solar cells, the photocurrent density in the bottom cell can be increased, requiring again optical optimization. Here, we analyse the effect of albedo, perovskite thickness and band gap as well as geographical location on the optical performance of these bi-facial perovskite/c-Si tandem solar cells. Our optical study shows that bi-facial 2T tandems, that also convert light incident from the rear, require radically thicker perovskite layers to match the additional current from the c-Si bottom cell. For typical perovskite bandgap and albedo values, even doubling the perovskite thickness is not sufficient. In this respect, lower bandgap perovskites are very interesting for application not only in bi-facial 2T tandems but also in related 3T and 4T tandems.

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Analysis of a Hybrid PV/T Concept Based on Wavelength Selective Films

ASME 2013 7th International Conference on Energy Sustainability ◽

10.1115/es2013-18011 ◽

2013 ◽

Cited By ~ 5

Author(s):

Tejas U. Ulavi ◽

Jane H. Davidson ◽

Tim Hebrink

Keyword(s):

Thin Film ◽

Monte Carlo ◽

Total Energy ◽

Ray Tracing ◽

Solar Spectrum ◽

Photovoltaic Module ◽

Optical Performance ◽

Technical Performance ◽

Compound Parabolic Concentrator ◽

Pv Modules

The technical performance of a non-tracking hybrid PV/T concept that uses a wavelength selective film is modeled. The wavelength selective film is coupled with a compound parabolic concentrator to reflect and concentrate the infrared portion of the solar spectrum onto a tubular absorber while transmitting the visible portion of the spectrum to an underlying thin-film photovoltaic module. The optical performance of the CPC/selective film is obtained through Monte Carlo Ray-Tracing. The CPC geometry is optimized for maximum total energy generation for a roof-top application. Applied to a rooftop in Phoenix, Arizona USA, the hybrid PV/T provides 20% more energy compared to a system of the same area with independent solar thermal and PV modules, but the increase is achieved at the expense of a decrease in the electrical efficiency from 8.8% to 5.8%.

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Silicon nanostructure-doped polymer/nematic liquid crystal composites for low voltage-driven smart windows

Nanotechnology ◽

10.1088/1361-6528/ac3a3b ◽

2021 ◽

Author(s):

Zemin He ◽

Ping Yu ◽

Huimin Zhang ◽

Yuzhen Zhao ◽

Yanfang Zhu ◽

...

Keyword(s):

Liquid Crystal ◽

Nematic Liquid Crystal ◽

Polymer Matrix ◽

Performance Test ◽

Low Voltage ◽

Sio2 Nanoparticles ◽

Silicon Nanostructures ◽

Driving Voltage ◽

Optical Performance ◽

Smart Windows

Abstract In this work, two silicon nanostructures were doped into polymer/nematic liquid crystal composites to regulate the electric-optical performance. Commercial SiO2 nanoparticles and synthesized thiol polyhedral oligomeric silsesquioxane (POSS-SH) were chosen as the dopants to afford the silicon nanostructures. SiO2 nanoparticles were physically dispersed in the composites and the nanostructure from POSS-SH was implanted into the polymer matrix of the composites via photoinduced thiol-ene crosslinking. SEM results indicated that the implantation of POSS microstructure into the polymer matrix was conducive to obtaining the uniform porous polymer microstructures in the composites while the introduction of SiO2 nanoparticles led to the loose and heterogeneous polymer morphologies. The electric-optical performance test results also demonstrated that the electric-optical performance regulation effect of POSS microstructure was more obvious than that of SiO2 nanoparticles. The driving voltage was reduced by almost 80% if the concentration of POSS-SH in the composite was nearly 8 wt% and the sample could be completely driven by the electric field whose voltage was lower than the safe voltage for continuous contact (24 V). This work could provide a creative approach for the regulation of electric-optical performance for polymer/nematic liquid crystal composites and the fabrication of low voltage-driven PDLC films for smart windows.

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Bio-inspired TiO2 nano-cone antireflection layer for the optical performance improvement of VO2 thermochromic smart windows

Scientific Reports ◽

10.1038/s41598-020-68411-6 ◽

2020 ◽

Vol 10 (1) ◽

Cited By ~ 1

Author(s):

Sai Liu ◽

Chi Yan Tso ◽

Hau Him Lee ◽

Yi Zhang ◽

Kin Man Yu ◽

...

Keyword(s):

Performance Improvement ◽

Optical Performance ◽

Smart Windows

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Analysis of a Hybrid PV/T Concept Based on Wavelength Selective Mirror Films

Journal of Solar Energy Engineering ◽

10.1115/1.4026678 ◽

2014 ◽

Vol 136 (3) ◽

Cited By ~ 8

Author(s):

Tejas U. Ulavi ◽

Jane H. Davidson ◽

Tim Hebrink

Keyword(s):

Thin Film ◽

Monte Carlo ◽

Total Energy ◽

Ray Tracing ◽

Solar Spectrum ◽

Photovoltaic Module ◽

Optical Performance ◽

Technical Performance ◽

Compound Parabolic Concentrator ◽

Pv Modules

The technical performance of a nontracking hybrid PV/T concept that uses a wavelength selective film is modeled. The wavelength selective film is coupled with a compound parabolic concentrator (CPC) to reflect and concentrate the infrared portion of the solar spectrum onto a tubular absorber while transmitting the visible portion of the spectrum to an underlying thin-film photovoltaic module. The optical performance of the CPC/selective film is obtained through Monte Carlo ray tracing (MCRT). The CPC geometry is optimized for maximum total energy generation for a roof-top application. Applied to a roof-top in Phoenix, AZ, the hybrid PV/T provides 20% more energy compared with a system of the same area with independent side-by-side solar thermal and PV modules, but the increase is achieved at the expense of a decrease in the electrical efficiency from 8.8% to 5.8%.

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Recent Advances in Fabrication of Flexible, Thermochromic Vanadium Dioxide Films for Smart Windows

Nanomaterials ◽

10.3390/nano11102674 ◽

2021 ◽

Vol 11 (10) ◽

pp. 2674

Author(s):

Jongbae Kim ◽

Taejong Paik

Keyword(s):

Thin Films ◽

Energy Saving ◽

Near Infrared ◽

Solar Spectrum ◽

Smart Windows ◽

Space Group ◽

Practical Applications ◽

Flexible Polymer ◽

Recent Advances ◽

Potential Applications

Monoclinic-phase VO2 (VO2(M)) has been extensively studied for use in energy-saving smart windows owing to its reversible insulator–metal transition property. At the critical temperature (Tc = 68 °C), the insulating VO2(M) (space group P21/c) is transformed into metallic rutile VO2 (VO2(R) space group P42/mnm). VO2(M) exhibits high transmittance in the near-infrared (NIR) wavelength; however, the NIR transmittance decreases significantly after phase transition into VO2(R) at a higher Tc, which obstructs the infrared radiation in the solar spectrum and aids in managing the indoor temperature without requiring an external power supply. Recently, the fabrication of flexible thermochromic VO2(M) thin films has also attracted considerable attention. These flexible films exhibit considerable potential for practical applications because they can be promptly applied to windows in existing buildings and easily integrated into curved surfaces, such as windshields and other automotive windows. Furthermore, flexible VO2(M) thin films fabricated on microscales are potentially applicable in optical actuators and switches. However, most of the existing fabrication methods of phase-pure VO2(M) thin films involve chamber-based deposition, which typically require a high-temperature deposition or calcination process. In this case, flexible polymer substrates cannot be used owing to the low-thermal-resistance condition in the process, which limits the utilization of flexible smart windows in several emerging applications. In this review, we focus on recent advances in the fabrication methods of flexible thermochromic VO2(M) thin films using vacuum deposition methods and solution-based processes and discuss the optical properties of these flexible VO2(M) thin films for potential applications in energy-saving smart windows and several other emerging technologies.

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Silicon heterojunction-based tandem solar cells: past, status, and future prospects

Nanophotonics ◽

10.1515/nanoph-2021-0034 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Xingliang Li ◽

Qiaojing Xu ◽

Lingling Yan ◽

Chengchao Ren ◽

Biao Shi ◽

...

Keyword(s):

Solar Cells ◽

Power Conversion ◽

Solar Spectrum ◽

Back Contact ◽

Optical Performance ◽

Future Prospects ◽

High Power Conversion Efficiency ◽

Comprehensive Overview ◽

Tandem Solar Cells ◽

Different Parts

Abstract Due to stable and high power conversion efficiency (PCE), it is expected that silicon heterojunction (SHJ) solar cells will dominate the photovoltaic market. So far, the highest PCE of the SHJ-interdigitated back contact (IBC) solar cells has reached 26.7%, approximately approaching the theoretical Shockley–Queisser (SQ) limitation of 29.4%. To break through this limit, multijunction devices consisting of two or three stacked subcells have been developed, which can fully utilize the sunlight by absorbing different parts of the solar spectrum. This article provides a comprehensive overview of current research on SHJ-based tandem solar cells (SHJ-TSCs), including perovskite/SHJ TSCs and III–V/SHJ TSCs. Firstly, we give a brief introduction to the structures of SHJ-TSCs, followed by a discussion of fabrication processes. Afterwards, we focus on various materials and processes that have been explored to optimize the electrical and optical performance. Finally, we highlight the opportunities and challenges of SHJ-TSCs, as well as personal perspectives on the future development directions in this field.

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Warm/cool-tone switchable thermochromic material for smart windows by orthogonally integrating properties of pillar[6]arene and ferrocene

Nature Communications ◽

10.1038/s41467-018-03827-3 ◽

2018 ◽

Vol 9 (1) ◽

Cited By ~ 72

Author(s):

Sai Wang ◽

Zuqiang Xu ◽

Tingting Wang ◽

Tangxin Xiao ◽

Xiao-Yu Hu ◽

...

Keyword(s):

Smart Windows ◽

Thermochromic Material

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Acid Solution Processed VO2-Based Composite Films with Enhanced Thermochromic Properties for Smart Windows

Materials ◽

10.3390/ma14174927 ◽

2021 ◽

Vol 14 (17) ◽

pp. 4927

Author(s):

Zhe Wang ◽

Bin Li ◽

Shouqin Tian ◽

Baoshun Liu ◽

Xiujian Zhao ◽

...

Keyword(s):

Acid Solution ◽

Near Infrared ◽

Composite Films ◽

Solution Process ◽

Localized Surface Plasmon ◽

Solar Modulation ◽

Smart Windows ◽

Nir Light ◽

Thermochromic Material ◽

Thermochromic Properties

As a typical thermochromic material, VO2 coatings can be applied to smart windows by modulating the transmission of near infrared (NIR) light via phase transition. However, the inherent undesirable luminous transmittance (Tlum) and solar modulation efficiency (ΔTsol) of pure VO2 impede its practical application. In order to solve this problem, the porous VO2 based composite film was prepared by magnetron sputtering and subsequent acid solution process with Zn2V2O7 particles used as a sacrificial template to create pores, which showed excellent Tlum (72.1%) and enhanced ΔTsol (10.7%) compared with pure VO2 film. It was demonstrated that the porous structure of the film caused by acid solution process could improve the Tlum obviously and the isolated VO2 nanoparticles presented strong localized surface plasmon resonance (LSPR) effects to enhance the ΔTsol. Therefore, this method will provide a facile way to prepare VO2 based films with excellent thermochromic performance and thus promote the application of the VO2 based films in smart windows.

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