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).

Hybrid Carbon Nanotube Networks as Efficient Hole Extraction Layers for Organic Photovoltaics

“…18 In this study, strong evidence for preferential hole transport in solution processable large area networks of polymer wrapped s-SWNT networks is presented, indicating the role of such nanohybrids as hole extraction layers. In order to investigate the nanohybrids to perform in the capacity of hole transport layers (HTL) in OPVs, devices were fabricated with rr-P3HT/sSWNTs as the HTL with rr-P3HT/PC 70 BM ( [6,6]-Phenyl-C71-butyric acid methyl ester) as the active photoabsorption layer.…”

Carbon nanomaterials for electronics, optoelectronics, photovoltaics, and sensing

“…363,364 CNTs have also been incorporated hierarchically between various layers of an OPV device, namely the anode, hole transport layer, bulk heterojunction active layer, and cathode. 365 It was observed that the presence of CNTs at the anode or hole transport layer were beneficial to the cell performance, improving PCE to 4.9% versus 4% for the control device. This improvement resulted from a reduction in the series resistance due to conductive pathways from interpenetrating CNTs in the hole transport layer.…”

Difluorobenzothiadiazole based two-dimensional conjugated polymers with triphenylamine substituted moieties as pendants for bulk heterojunction solar cells

“…Thus, there must have been a relatively strong driving force for dissociation of excitons at the BHJ interface of the PBTFA13/PC 61 BM blend. Consequently, the lower degree of charge recombination loss resulted in the relatively higher values of V OC for the PSCs based on the PBTFA13/PC 61 BM blend films [55,56]. Moreover, the values of J SC of the PSCs incorporating PBTFA13/PC 61 BM blends were higher than those of the PSCs based on PBTFA12/PC 61 BM and PBTFA11/PC 61 BM.…”