Issue 15, 2015

Precision printing and optical modeling of ultrathin SWCNT/C60 heterojunction solar cells

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.

Graphical abstract: Precision printing and optical modeling of ultrathin SWCNT/C60 heterojunction solar cells

Supplementary files

Article information

Article type
Paper
Submitted
10 Jan 2015
Accepted
11 Feb 2015
First published
16 Mar 2015

Nanoscale, 2015,7, 6556-6566

Author version available

Precision printing and optical modeling of ultrathin SWCNT/C60 heterojunction solar cells

S. L. Guillot, K. S. Mistry, A. D. Avery, J. Richard, A. Dowgiallo, P. F. Ndione, J. van de Lagemaat, M. O. Reese and J. L. Blackburn, Nanoscale, 2015, 7, 6556 DOI: 10.1039/C5NR00205B

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