Toward efficient and omnidirectional n-type si solar cells: Concurrent improvement in optical and electrical characteristics by employing microscale hierarchical structures

Hsin Ping Wang, Tzu Yin Lin, Meng Lin Tsai, Wei Chen Tu, Ming Yi Huang, Chee Wee Liu, Yu Lun Chueh*, Jr-Hau He

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)2959-2969
Number of pages11
JournalACS Nano
Volume8
Issue number3
DOIs
StatePublished - Mar 25 2014

Keywords

  • Si heterojunction solar cells
  • light-scattering
  • microscaled hierarchical structure
  • omnidirectional n-type Si solar cells

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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