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Title: Critical role of the sorting polymer in carbon nanotube-based minority carrier devices

A prerequisite for carbon nanotube-based optoelectronic devices is the ability to sort them into a pure semiconductor phase. One of the most common sorting routes is enabled through using specific wrapping polymers. Here we show that subtle changes in the polymer structure can have a dramatic influence on the figures of merit of a carbon nanotube-based photovoltaic device. By comparing two commonly used polyfluorenes (PFO and PFO-BPy) for wrapping (7,5) and (6,5) chirality SWCNTs, we demonstrate that they have contrasting effects on the device efficiency. We attribute this to the differences in their ability to efficiently transfer charge. Although PFO may act as an efficient interfacial layer at the anode, PFO-BPy, having the additional pyridine side groups, forms a high resistance layer degrading the device efficiency. By comparing PFO|C 60 and C 60-only devices, we found that presence of a PFO layer at low optical densities resulted in the increase of all three solar cell parameters, giving nearly an order of magnitude higher efficiency over that of C 60-only devices. In addition, with a relatively higher contribution to photocurrent from the PFO-C 60 interface, an open circuit voltage of 0.55 V was obtained for PFO-(7,5)-C 60 devices. On the othermore » hand, PFO-BPy does not affect the open circuit voltage but drastically reduces the short circuit current density. Lastly, these results indicate that the charge transport properties and energy levels of the sorting polymers have to be taken into account to fully understand their effect on carbon nanotube-based solar cells.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3] ; ORCiD logo [2] ; ORCiD logo [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Indian Institute of Technology Guwahati, Assam (India)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
NREL/JA-5900-67220
Journal ID: ISSN 1936-0851
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 10; Journal Issue: 12; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 77 NANOSCIENCE AND NANOTECHNOLOGY; carbon nanotubes layer; single chirality; polymer wrapping; polyfluorenes; solar cell
OSTI Identifier:
1340642