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Publications
Nayeun Lee; Muyu Xue; Jiho Hong; Jorik van de Groep; Mark L Brongersma
Multi‐resonant Mie Resonator Arrays for Broadband Light Trapping in Ultrathin c‐Si Solar Cells Journal Article
In: Advanced Materials, pp. 2210941, 2023.
@article{lee2023multi,
title = {Multi‐resonant Mie Resonator Arrays for Broadband Light Trapping in Ultrathin c‐Si Solar Cells},
author = {Nayeun Lee and Muyu Xue and Jiho Hong and Jorik van de Groep and Mark L Brongersma},
doi = {10.1002/adma.202210941},
year = {2023},
date = {2023-05-02},
urldate = {2023-05-02},
journal = {Advanced Materials},
pages = {2210941},
abstract = {Effective photon management is critical to realize high power conversion efficiencies for thin crystalline Si (c-Si) solar cells. Standard few-100-µm-thick bulk cells achieve light trapping with macroscopic surface textures covered by thin, continuous antireflection coatings. Such sizeable textures are challenging to implement on ultrathin cells. Here, we illustrate how nanoscale Mie-resonator-arrays with a bi-modal size distribution support multiple resonances that can work in concert to achieve simultaneous antireflection and light-trapping across the broad solar spectrum. We experimentally demonstrate the effectiveness of these light-trapping antireflection coatings (LARCs) on a 2.8-µm-thick c-Si solar cell. The measured short-circuit current and corresponding power conversion efficiency are notably improved, achieving efficiencies as high as 11.2%. Measurements of the saturation current density on completed cells indicate that thermal oxides can effectively limit surface recombination. The presented design principles are applicable to a wide range of solar cells.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Effective photon management is critical to realize high power conversion efficiencies for thin crystalline Si (c-Si) solar cells. Standard few-100-µm-thick bulk cells achieve light trapping with macroscopic surface textures covered by thin, continuous antireflection coatings. Such sizeable textures are challenging to implement on ultrathin cells. Here, we illustrate how nanoscale Mie-resonator-arrays with a bi-modal size distribution support multiple resonances that can work in concert to achieve simultaneous antireflection and light-trapping across the broad solar spectrum. We experimentally demonstrate the effectiveness of these light-trapping antireflection coatings (LARCs) on a 2.8-µm-thick c-Si solar cell. The measured short-circuit current and corresponding power conversion efficiency are notably improved, achieving efficiencies as high as 11.2%. Measurements of the saturation current density on completed cells indicate that thermal oxides can effectively limit surface recombination. The presented design principles are applicable to a wide range of solar cells.
Nayeun Lee
Nanophotonics enhanced optoelectronic devices : from photovoltaics to imaging PhD Thesis
Stanford University, 2023.
@phdthesis{nayeunleethesis,
title = {Nanophotonics enhanced optoelectronic devices : from photovoltaics to imaging},
author = {Nayeun Lee},
url = {http://purl.stanford.edu/md716fk1989},
year = {2023},
date = {2023-03-28},
urldate = {2023-03-28},
address = {Stanford, CA, US},
school = {Stanford University},
abstract = {Next-generation optoelectronic devices are required to be more compact and light-weight, and to achieve new optical functionalities at the same time. While these are challenging for current hardware designs, nanophotonics can be a key strategy to realize an optoelectronic device with desired functions in a smaller form factor. In this work, we will explore how nanophotonics can be leveraged to enhance the performance of optoelectronic devices, focusing on photovoltaics and imaging application. In the first part, we will see how we can design a thin, single layer of nanostructures that can function as both antireflection coating and light-trapping layer. We will experimentally demonstrate the effectiveness of these light-trapping antireflection coatings (LARCs) on 2.8-µm-thick c-Si solar cells and notably improve the efficiencies. In the second part, we will present a new type of imaging technology that can discern surface textures by utilizing a set of metasurface-driven pixels (i.e. meta-pixels). The metasurfaces in each type of pixel are engineered to achieve desired angular sensitivities, which enable efficient perception of texture. Furthermore, we will experimentally demonstrate the meta-pixels and show their efficacy through reconstructed texture images that effectively visualize differences in textures.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
Next-generation optoelectronic devices are required to be more compact and light-weight, and to achieve new optical functionalities at the same time. While these are challenging for current hardware designs, nanophotonics can be a key strategy to realize an optoelectronic device with desired functions in a smaller form factor. In this work, we will explore how nanophotonics can be leveraged to enhance the performance of optoelectronic devices, focusing on photovoltaics and imaging application. In the first part, we will see how we can design a thin, single layer of nanostructures that can function as both antireflection coating and light-trapping layer. We will experimentally demonstrate the effectiveness of these light-trapping antireflection coatings (LARCs) on 2.8-µm-thick c-Si solar cells and notably improve the efficiencies. In the second part, we will present a new type of imaging technology that can discern surface textures by utilizing a set of metasurface-driven pixels (i.e. meta-pixels). The metasurfaces in each type of pixel are engineered to achieve desired angular sensitivities, which enable efficient perception of texture. Furthermore, we will experimentally demonstrate the meta-pixels and show their efficacy through reconstructed texture images that effectively visualize differences in textures.
Jiho Hong; Jorik van de Groep; Nayeun Lee; Soo Jin Kim; Philippe Lalanne; Pieter G. Kik; Mark L. Brongersma
Nonlocal metasurface for circularly polarized light detection Journal Article
In: Optica, vol. 10, no. 1, pp. 134-141, 2023.
@article{Hong:23,
title = {Nonlocal metasurface for circularly polarized light detection},
author = {Jiho Hong and Jorik van de Groep and Nayeun Lee and Soo Jin Kim and Philippe Lalanne and Pieter G. Kik and Mark L. Brongersma},
doi = {10.1364/OPTICA.468252},
year = {2023},
date = {2023-01-20},
journal = {Optica},
volume = {10},
number = {1},
pages = {134-141},
abstract = {Modern-day sensing and imaging applications increasingly rely on accurate measurements of the primary physical quantities associated with light waves: intensity, wavelength, directionality, and polarization. These are conventionally performed with a series of bulky optical elements, but recently, it has been recognized that optical resonances in nanostructures can be engineered to achieve selective photodetection of light waves with a specific set of predetermined properties. Here, we theoretically illustrate how a thin silicon layer can be patterned into a dislocated nanowire-array that affords detection of circularly polarized light with an efficiency that reaches the theoretical limit for circular dichroism of a planar detector in a symmetric external environment. The presence of a periodic arrangement of dislocations is essential in achieving such unparalleled performance as they enable selective excitation of nonlocal, guided-mode resonances for one handedness of light. We also experimentally demonstrate compact, high-performance chiral photodetectors created from these dislocated nanowire-arrays. This work highlights the critical role defects can play in enabling new nanophotonic functions and devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Modern-day sensing and imaging applications increasingly rely on accurate measurements of the primary physical quantities associated with light waves: intensity, wavelength, directionality, and polarization. These are conventionally performed with a series of bulky optical elements, but recently, it has been recognized that optical resonances in nanostructures can be engineered to achieve selective photodetection of light waves with a specific set of predetermined properties. Here, we theoretically illustrate how a thin silicon layer can be patterned into a dislocated nanowire-array that affords detection of circularly polarized light with an efficiency that reaches the theoretical limit for circular dichroism of a planar detector in a symmetric external environment. The presence of a periodic arrangement of dislocations is essential in achieving such unparalleled performance as they enable selective excitation of nonlocal, guided-mode resonances for one handedness of light. We also experimentally demonstrate compact, high-performance chiral photodetectors created from these dislocated nanowire-arrays. This work highlights the critical role defects can play in enabling new nanophotonic functions and devices.
Koosha Nassiri Nazif; Alwin Daus; Jiho Hong; Nayeun Lee; Sam Vaziri; Aravindh Kumar; Frederick Nitta; Michelle E Chen; Siavash Kananian; Raisul Islam; Kwan-Ho Kim; Jin-Hong Park; Ada SY Poon; Mark L. Brongersma; Eric Pop; Krishna C. Saraswat
High-specific-power flexible transition metal dichalcogenide solar cells Journal Article
In: Nature Communications, vol. 12, iss. 1, pp. 1-9, 2021.
@article{nassiri2021highb,
title = {High-specific-power flexible transition metal dichalcogenide solar cells},
author = {Koosha Nassiri Nazif and Alwin Daus and Jiho Hong and Nayeun Lee and Sam Vaziri and Aravindh Kumar and Frederick Nitta and Michelle E Chen and Siavash Kananian and Raisul Islam and Kwan-Ho Kim and Jin-Hong Park and Ada SY Poon and Mark L. Brongersma and Eric Pop and Krishna C. Saraswat},
doi = {10.1038/s41467-021-27195-7},
year = {2021},
date = {2021-12-09},
journal = {Nature Communications},
volume = {12},
issue = {1},
pages = {1-9},
abstract = {Semiconducting transition metal dichalcogenides (TMDs) are promising for flexible high-specific-power photovoltaics due to their ultrahigh optical absorption coefficients, desirable band gaps and self-passivated surfaces. However, challenges such as Fermi-level pinning at the metal contact\textendashTMD interface and the inapplicability of traditional doping schemes have prevented most TMD solar cells from exceeding 2% power conversion efficiency (PCE). In addition, fabrication on flexible substrates tends to contaminate or damage TMD interfaces, further reducing performance. Here, we address these fundamental issues by employing: (1) transparent graphene contacts to mitigate Fermi-level pinning, (2) MoOx capping for doping, passivation and anti-reflection, and (3) a clean, non-damaging direct transfer method to realize devices on lightweight flexible polyimide substrates. These lead to record PCE of 5.1% and record specific power of 4.4 W g−1 for flexible TMD (WSe2) solar cells, the latter on par with prevailing thin-film solar technologies cadmium telluride, copper indium gallium selenide, amorphous silicon and III-Vs. We further project that TMD solar cells could achieve specific power up to 46 W g−1, creating unprecedented opportunities in a broad range of industries from aerospace to wearable and implantable electronics.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Semiconducting transition metal dichalcogenides (TMDs) are promising for flexible high-specific-power photovoltaics due to their ultrahigh optical absorption coefficients, desirable band gaps and self-passivated surfaces. However, challenges such as Fermi-level pinning at the metal contact–TMD interface and the inapplicability of traditional doping schemes have prevented most TMD solar cells from exceeding 2% power conversion efficiency (PCE). In addition, fabrication on flexible substrates tends to contaminate or damage TMD interfaces, further reducing performance. Here, we address these fundamental issues by employing: (1) transparent graphene contacts to mitigate Fermi-level pinning, (2) MoOx capping for doping, passivation and anti-reflection, and (3) a clean, non-damaging direct transfer method to realize devices on lightweight flexible polyimide substrates. These lead to record PCE of 5.1% and record specific power of 4.4 W g−1 for flexible TMD (WSe2) solar cells, the latter on par with prevailing thin-film solar technologies cadmium telluride, copper indium gallium selenide, amorphous silicon and III-Vs. We further project that TMD solar cells could achieve specific power up to 46 W g−1, creating unprecedented opportunities in a broad range of industries from aerospace to wearable and implantable electronics.
Nayeun Lee; Reehyang Kim; Ju Young Kim; Jong Beom Ko; Sang-Hee Ko Park; Sang Ouk Kim; Mark L. Brongersma; Jonghwa Shin
Self-Assembled Nano–Lotus Pod Metasurface for Light Trapping Journal Article
In: ACS Photonics, vol. 8, no. 6, pp. 1616–1622, 2021.
@article{lee2021self,
title = {Self-Assembled Nano\textendashLotus Pod Metasurface for Light Trapping},
author = {Nayeun Lee and Reehyang Kim and Ju Young Kim and Jong Beom Ko and Sang-Hee Ko Park and Sang Ouk Kim and Mark L. Brongersma and Jonghwa Shin},
doi = {10.1021/acsphotonics.0c01882},
year = {2021},
date = {2021-05-19},
journal = {ACS Photonics},
volume = {8},
number = {6},
pages = {1616\textendash1622},
abstract = {Concentration of electromagnetic waves in deep-subwavelength volumes has been widely investigated as a direct way of enhancing light-matter interactions. However, a homogeneous array of subwavelength nanogaps suitable for visible light localization and enhancement is difficult to realize due to the limitations of conventional lithography techniques. Here, a uniform array of ultrasmall plasmonic resonators with precisely controlled nanogaps (“nano\textendashlotus pods”) is presented for the visible light confinement and realized without any photo- or beam-based lithography steps. The unit motif of this metasurface with a physical volume of 52 × 60 × 40 nm3 is designed to resonantly trap visible light into an effective mode volume of 1.57 × 10\textendash5λ03. Each nano\textendashlotus pod can be considered as a curved metal\textendashinsulator\textendashmetal waveguide which exposes both of its end faces and thus hot spots with the strongest electric fields on the outermost flat surface. To realize this unique nanostructure, a template-stripping method is employed in conjunction with block copolymer self-assembly and atomic layer deposition which guarantee a homogeneous array over large areas. It is experimentally demonstrated that the proposed metasurface can be used as a highly uniform and flat substrate for surface-enhanced Raman spectroscopy of various analytes, especially a stiff two-dimensional material.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Concentration of electromagnetic waves in deep-subwavelength volumes has been widely investigated as a direct way of enhancing light-matter interactions. However, a homogeneous array of subwavelength nanogaps suitable for visible light localization and enhancement is difficult to realize due to the limitations of conventional lithography techniques. Here, a uniform array of ultrasmall plasmonic resonators with precisely controlled nanogaps (“nano–lotus pods”) is presented for the visible light confinement and realized without any photo- or beam-based lithography steps. The unit motif of this metasurface with a physical volume of 52 × 60 × 40 nm3 is designed to resonantly trap visible light into an effective mode volume of 1.57 × 10–5λ03. Each nano–lotus pod can be considered as a curved metal–insulator–metal waveguide which exposes both of its end faces and thus hot spots with the strongest electric fields on the outermost flat surface. To realize this unique nanostructure, a template-stripping method is employed in conjunction with block copolymer self-assembly and atomic layer deposition which guarantee a homogeneous array over large areas. It is experimentally demonstrated that the proposed metasurface can be used as a highly uniform and flat substrate for surface-enhanced Raman spectroscopy of various analytes, especially a stiff two-dimensional material.
Koosha Nassiri Nazif; Aravindh Kumar; Jiho Hong; Nayeun Lee; Raisul Islam; Connor J McClellan; Ouri Karni; Jorik van de Groep; Tony F Heinz; Eric Pop; Mark L Brongersma; Krishna C Saraswat
High-Performance p–n Junction Transition Metal Dichalcogenide Photovoltaic Cells Enabled by MoOx Doping and Passivation Journal Article
In: Nano Letters, vol. 21, no. 8, pp. 3443–3450, 2021.
@article{nassiri2021high,
title = {High-Performance p\textendashn Junction Transition Metal Dichalcogenide Photovoltaic Cells Enabled by MoOx Doping and Passivation},
author = {Koosha Nassiri Nazif and Aravindh Kumar and Jiho Hong and Nayeun Lee and Raisul Islam and Connor J McClellan and Ouri Karni and Jorik van de Groep and Tony F Heinz and Eric Pop and Mark L Brongersma and Krishna C Saraswat},
doi = {10.1021/acs.nanolett.1c00015},
year = {2021},
date = {2021-04-14},
journal = {Nano Letters},
volume = {21},
number = {8},
pages = {3443\textendash3450},
abstract = {Layered semiconducting transition metal dichalcogenides (TMDs) are promising materials for high-specific-power photovoltaics due to their excellent optoelectronic properties. However, in practice, contacts to TMDs have poor charge carrier selectivity, while imperfect surfaces cause recombination, leading to a low open-circuit voltage (VOC) and therefore limited power conversion efficiency (PCE) in TMD photovoltaics. Here, we simultaneously address these fundamental issues with a simple MoOx (x ≈ 3) surface charge-transfer doping and passivation method, applying it to multilayer tungsten disulfide (WS2) Schottky-junction solar cells with initially near-zero VOC. Doping and passivation turn these into lateral p\textendashn junction photovoltaic cells with a record VOC of 681 mV under AM 1.5G illumination, the highest among all p\textendashn junction TMD solar cells with a practical design. The enhanced VOC also leads to record PCE in ultrathin (\<90 nm) WS2 photovoltaics. This easily scalable doping and passivation scheme is expected to enable further advances in TMD electronics and optoelectronics.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Layered semiconducting transition metal dichalcogenides (TMDs) are promising materials for high-specific-power photovoltaics due to their excellent optoelectronic properties. However, in practice, contacts to TMDs have poor charge carrier selectivity, while imperfect surfaces cause recombination, leading to a low open-circuit voltage (VOC) and therefore limited power conversion efficiency (PCE) in TMD photovoltaics. Here, we simultaneously address these fundamental issues with a simple MoOx (x ≈ 3) surface charge-transfer doping and passivation method, applying it to multilayer tungsten disulfide (WS2) Schottky-junction solar cells with initially near-zero VOC. Doping and passivation turn these into lateral p–n junction photovoltaic cells with a record VOC of 681 mV under AM 1.5G illumination, the highest among all p–n junction TMD solar cells with a practical design. The enhanced VOC also leads to record PCE in ultrathin (<90 nm) WS2 photovoltaics. This easily scalable doping and passivation scheme is expected to enable further advances in TMD electronics and optoelectronics.
