Toward efficient and omnidirectional n-type si solar cells: Concurrent improvement in optical and electrical characteristics by employing microscale hierarchical structures
Journal
ACS Nano
Journal Volume
8
Journal Issue
3
Pages
2959-2969
Date Issued
2014
Author(s)
Wang, H.-P.
Lin, T.-Y.
Tsai, M.-L.
Tu, W.-C.
Huang, M.-Y.
Liu, C.-W.
Chueh, Y.-L.
He, J.-H.
Abstract
We demonstrated that hierarchical structures combining different scales (i.e., pyramids from 1.5 to 7.5 μm in width on grooves from 40 to 50 μm in diameter) exhibit excellent broadband and omnidirectional light-trapping characteristics. These microscaled hierarchical structures could not only improve light absorption but prevent poor electrical properties typically observed from nanostructures (e.g., ultra-high-density surface defects and nonconformal deposition of following layers, causing low open-circuit voltages and fill factors). The microscaled hierarchical Si heterojunction solar cells fabricated with hydrogenated amorphous Si layers on as-cut Czochralski n-type substrates show a high short-circuit current density of 36.4 mA/cm2, an open-circuit voltage of 607 mV, and a conversion efficiency of 15.2% due to excellent antireflection and light-scattering characteristics without sacrificing minority carrier lifetimes. Compared to cells with grooved structures, hierarchical heterojunction solar cells exhibit a daily power density enhancement (69%) much higher than the power density enhancement at normal angle of incidence (49%), demonstrating omnidirectional photovoltaic characteristics of hierarchical structures. Such a concept of hierarchical structures simultaneously improving light absorption and photocarrier collection efficiency opens avenues for developing large-area and cost-effective solar energy devices in the industry. © 2014 American Chemical Society.
Subjects
light-scattering; microscaled hierarchical structure; omnidirectional n-type Si solar cells; Si heterojunction solar cells
SDGs
Other Subjects
Amorphous silicon; Electric properties; Heterojunctions; Light absorption; Light scattering; Open circuit voltage; Silicon; Solar energy; Tracking (position); Angle of Incidence; Collection efficiency; Electrical characteristic; Heterojunction solar cells; Hierarchical structures; Minority carrier lifetimes; Photovoltaic characteristics; Si solar cells; Silicon solar cells
Type
journal article