Precision Printing and Optical Modeling of Ultrathin SWCNT/C60 Heterojunction Solar Cells

Sarah L. Guillot, Kevin S. Mistry, Azure D. Avery, Jonah Richard, Anne Marie Dowgiallo, Paul F. Ndione, Jao Van De Lagemaat, Matthew O. Reese, Jeffrey L. Blackburn

Research output: Contribution to journalArticlepeer-review

40 Scopus Citations

Abstract

Semiconducting single-walled carbon nanotubes (s-SWCNTs) are promising candidates as the active layer in photovoltaics (PV), particularly for niche applications where high infrared absorbance and/or semi-transparent solar cells are desirable. Most current fabrication strategies for SWCNT PV devices suffer from relatively high surface roughness and lack nanometer-scale deposition precision, both of which may hamper the reproducible production of ultrathin devices. Additionally, detailed optical models of SWCNT PV devices are lacking, due in part to a lack of well-defined optical constants for high-purity s-SWCNT thin films. Here, we present an optical model that accurately reconstructs the shape and magnitude of spectrally resolved external quantum efficiencies for ultrathin (7,5) s-SWCNT/C60 solar cells that are deposited by ultrasonic spraying. The ultrasonic spraying technique enables thickness tuning of the s-SWCNT layer with nanometer-scale precision, and consistently produces devices with low s-SWCNT film average surface roughness (Rq of <5 nm). Our optical model, based entirely on measured optical constants of each layer within the device stack, enables quantitative predictions of thickness-dependent relative photocurrent contributions of SWCNTs and C60 and enables estimates of the exciton diffusion lengths within each layer. These results establish routes towards rational performance improvements and scalable fabrication processes for ultra-thin SWCNT-based solar cells.

Original languageAmerican English
Pages (from-to)6556-6566
Number of pages11
JournalNanoscale
Volume7
Issue number15
DOIs
StatePublished - 2015

Bibliographical note

Publisher Copyright:
© The Royal Society of Chemistry.

NREL Publication Number

  • NREL/JA-5900-63523

Keywords

  • exciton
  • optical modeling
  • photovoltaic
  • single-walled carbon nanotube

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