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Inverted Silicon Nanopencil Array Solar Cells with Enhanced Contact Structures

View Article: PubMed Central - PubMed

ABSTRACT

Although three-dimensional nanostructured solar cells have attracted extensive research attention due to their superior broadband and omnidirectional light-harvesting properties, majority of them are still suffered from complicated fabrication processes as well as disappointed photovoltaic performances. Here, we employed our newly-developed, low-cost and simple wet anisotropic etching to fabricate hierarchical silicon nanostructured arrays with different solar cell contact design, followed by systematic investigations of their photovoltaic characteristics. Specifically, nano-arrays with the tapered tips (e.g. inverted nanopencils) are found to enable the more conformal top electrode deposition directly onto the nanostructures for better series and shunt conductance, but its insufficient film coverage at the basal plane would still restrict the charge carrier collection. In contrast, the low-platform contact design facilitates a substantial photovoltaic device performance enhancement of ~24%, as compared to the one of conventional top electrode design, due to the shortened current path and improved lateral conductance for the minimized carrier recombination and series resistance. This enhanced contact structure can not only maintain excellent photon-trapping behaviors of nanostructures, but also help to eliminate adverse impacts of these tapered nano-morphological features on the contact resistance, providing further insight into design consideration in optimizing the contact geometry for high-performance nanostructured photovoltaic devices.

No MeSH data available.


Schematic illustration and 45° angle-view SEM images of different top electrode contact design with (a) metal directly deposited on top of the structure, (b) mesa bar metal strips and (c) low-platform metal strips before the metal stack deposition. It is noted that nanopencil arrays are employed here due to their observed superior light absorption characteristics for the improved PCE of fabricated solar devices. Schematics are not drawn in scale.
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f4: Schematic illustration and 45° angle-view SEM images of different top electrode contact design with (a) metal directly deposited on top of the structure, (b) mesa bar metal strips and (c) low-platform metal strips before the metal stack deposition. It is noted that nanopencil arrays are employed here due to their observed superior light absorption characteristics for the improved PCE of fabricated solar devices. Schematics are not drawn in scale.

Mentions: With the aim to enhance the charge collection efficiency, we purposely propose and fabricate several enhanced contact structures, which can spatially separate the nanostructured window layer and mesa bar contact with small area such that the photo-carrier generation and collection are decoupled from each other. Specifically, by combining MaCE, nanosphere lithography and conventional photolithography, hierarchically arranged Si nanopecil arrays can be achieved as depicted in Fig. 4 23. Nanopencil arrays are exploited here due to their observed superior light absorption characteristics for the improved PCE of fabricated solar devices. Figure 4a shows the SEM image of the fabricated nanopencil arrays while Fig. 4b,c display the top electrode region of the mesa bar and low-platform contact structures, respectively, before the metal stack deposition. It is noticed that these hierarchically arranged nanopencil arrays fabricated for the mesa bar and low-platform contacts can be readily obtained by changing the sequence of lithographic processes in order to achieve the site-selective etching and fabrication of nanostructured arrays23. For instance, before the nanosphere lithography, the mesa bar feature could be first pre-patterned onto the silicon surface by conventional photolithographic, sputtering and lift-off processes; this way, after the catalyst deposition and anisotropic wet etching were performed, the nanopencil arrays as well as the mesa bar contact structure could be attained simultaneously for the solar cell fabrication (Fig. 4b). Similarly, to achieve the low-platform contact scheme, the patterned catalyst nanomesh was instead first patterned onto the silicon surface by nanosphere lithography, followed by Au deposition on the defined contact region served as catalysts for the subsequent etching (Fig. 4c).


Inverted Silicon Nanopencil Array Solar Cells with Enhanced Contact Structures
Schematic illustration and 45° angle-view SEM images of different top electrode contact design with (a) metal directly deposited on top of the structure, (b) mesa bar metal strips and (c) low-platform metal strips before the metal stack deposition. It is noted that nanopencil arrays are employed here due to their observed superior light absorption characteristics for the improved PCE of fabricated solar devices. Schematics are not drawn in scale.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037459&req=5

f4: Schematic illustration and 45° angle-view SEM images of different top electrode contact design with (a) metal directly deposited on top of the structure, (b) mesa bar metal strips and (c) low-platform metal strips before the metal stack deposition. It is noted that nanopencil arrays are employed here due to their observed superior light absorption characteristics for the improved PCE of fabricated solar devices. Schematics are not drawn in scale.
Mentions: With the aim to enhance the charge collection efficiency, we purposely propose and fabricate several enhanced contact structures, which can spatially separate the nanostructured window layer and mesa bar contact with small area such that the photo-carrier generation and collection are decoupled from each other. Specifically, by combining MaCE, nanosphere lithography and conventional photolithography, hierarchically arranged Si nanopecil arrays can be achieved as depicted in Fig. 4 23. Nanopencil arrays are exploited here due to their observed superior light absorption characteristics for the improved PCE of fabricated solar devices. Figure 4a shows the SEM image of the fabricated nanopencil arrays while Fig. 4b,c display the top electrode region of the mesa bar and low-platform contact structures, respectively, before the metal stack deposition. It is noticed that these hierarchically arranged nanopencil arrays fabricated for the mesa bar and low-platform contacts can be readily obtained by changing the sequence of lithographic processes in order to achieve the site-selective etching and fabrication of nanostructured arrays23. For instance, before the nanosphere lithography, the mesa bar feature could be first pre-patterned onto the silicon surface by conventional photolithographic, sputtering and lift-off processes; this way, after the catalyst deposition and anisotropic wet etching were performed, the nanopencil arrays as well as the mesa bar contact structure could be attained simultaneously for the solar cell fabrication (Fig. 4b). Similarly, to achieve the low-platform contact scheme, the patterned catalyst nanomesh was instead first patterned onto the silicon surface by nanosphere lithography, followed by Au deposition on the defined contact region served as catalysts for the subsequent etching (Fig. 4c).

View Article: PubMed Central - PubMed

ABSTRACT

Although three-dimensional nanostructured solar cells have attracted extensive research attention due to their superior broadband and omnidirectional light-harvesting properties, majority of them are still suffered from complicated fabrication processes as well as disappointed photovoltaic performances. Here, we employed our newly-developed, low-cost and simple wet anisotropic etching to fabricate hierarchical silicon nanostructured arrays with different solar cell contact design, followed by systematic investigations of their photovoltaic characteristics. Specifically, nano-arrays with the tapered tips (e.g. inverted nanopencils) are found to enable the more conformal top electrode deposition directly onto the nanostructures for better series and shunt conductance, but its insufficient film coverage at the basal plane would still restrict the charge carrier collection. In contrast, the low-platform contact design facilitates a substantial photovoltaic device performance enhancement of ~24%, as compared to the one of conventional top electrode design, due to the shortened current path and improved lateral conductance for the minimized carrier recombination and series resistance. This enhanced contact structure can not only maintain excellent photon-trapping behaviors of nanostructures, but also help to eliminate adverse impacts of these tapered nano-morphological features on the contact resistance, providing further insight into design consideration in optimizing the contact geometry for high-performance nanostructured photovoltaic devices.

No MeSH data available.