title: Hierarchical placement and associated optoelectronic impact of carbon nanotubes in polymer-fullerene solar cells.
abstract: Since their discovery, carbon nanotubes (CNTs) have been considered to be promising candidates for polymer-based solar cells, but their functional incorporation and utilization in such devices have been limited due to processing bottlenecks. Here, we demonstrate the realization of controlled placement of a single-walled CNT (SWNT) monolayer network at four different positions in polymer-fullerene bulk-heterojunction (BHJ) solar cells. SWNTs were deposited by dip-coating from a hydrophilic suspension, and a very brief, largely nondestructive argon plasma treatment of the active layer was utilized for incorporation of a SWNT layer within or above it. We demonstrate that SWNTs on the hole-collection side of the active layer lead to an increase in power conversion efficiency (PCE) of the photovoltaic devices from 4 to 4.9% (under AM 1.5 G, 1.3 suns illumination). This is the highest reported PCE for polymer-based solar cells incorporating CNTs, upon consideration of expected scaling of device parameters for 1 sun illumination. We also observe that SWNTs deposited on the top of the active layer lead to major electro-optical changes in the device functionality, including an increased fluorescence lifetime of poly-3-hexylthiophene (P3HT).
authors.affiliation: Department of Electrical Engineering and Chemistry Department, University of California, Riverside, California 92521, USA.
authors.forename: Sumit
authors.initials: S
authors.lastname: Chaudhary
authors.forename: Haiwei
authors.initials: H
authors.lastname: Lu
authors.forename: Astrid M
authors.initials: AM
authors.lastname: Müller
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Bardeen
authors.forename: Mihrimah
authors.initials: M
authors.lastname: Ozkan
mesh_terms: D004563:Electrochemistry; D037741:Fullerenes / Q000737:chemistry*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010777:Photochemistry; D011108:Polymers / Q000737:chemistry*; D012993:Solar Energy
chemical_list: D037741:Fullerenes; D037742:Nanotubes, Carbon; D011108:Polymers