Carbon Nanotubes for Photovoltaics: From Lab to Industry

Abstract

All other nanotube conformations (0° < θ < 30°) are referred to as being chiral. In this 1D system, circumferential electron confinement results in SWCNTs that are either metallic (m) or semiconducting (s) and the innate ability of small changes in diameter to impart large changes in the spectral position (size) of absorption maxima (bandgap) of the SWCNTs. [1a,2] For each chiral species these maxima appear as sets of discrete excitonic transitions (S 11 , S 22 , S 33 …etc.) in the infrared, visible, and ultraviolet and the ability to tune them with structure has made SWCNTs one of the most intensively studied nanomaterials of the past two decades. [3] SWCNTs meet all of the requirements for next generation technology to become flexible and potentially made entirely from carbon to aid disposal at the end of the product life-cycle. Applications for SWCNTs can be found across all fields of science including photonics, [4] telecommunications, [5] batteries, [6] fuel cells, [7] high frequency transistors, [8] biosensors, [9] novel memory devices, [10] molecular contacts, [11] and cancer research. [12] In particular, their chirality dependent bandgap, chemical stability, conductivity, and hole selectivity have made them attractive for new generation solar cells and light sensitive elements. [13] For example, there are 200 species in the dia meter range of 0.6-2 nm, which have first (S 11) and second (S 22) optical transitions ranging from 2.57 eV (visible) to 0.5 eV (near-infrared) and these already cover a majority of the solar spectrum (400-2000 nm), Figure 1d. [14] Being solutionprocessable and fiber-shaped, CNTs can easily be integrated into different types of solar cells with distinct functions. For example, as a photoactive layer in organic solar cell, a transparent electrode in silicon and perovskite solar cells or as counter electrode in dye-sensitized solar cells. [15] However, despite their promise, the number of real-world applications for SWCNTs in the photovoltaics (PV) industry continue to remain limited. The reasons for this are manifold and include the comparatively lower power conversion efficiency (PCE) and device area of SWCNT-based technologies, which drive simple cost-benefit arguments to retool existing production lines, ongoing challenges to orientate and control the structure of CNT films in a scalable manner, spurious health concerns associated with the use of CNTs [16] and importantly, the fact that it is still not possible to selectively synthesize SWCNTs of arbitrarily defined chirality. Most synthesis methods produce a 2:1 mixture of many semiconducting and metallic chiral types and even the CoMoCAT synthesis process, [17] which is well known to be highly enriched in small diameter (6,5), still contains at least 15 other chiral species in low concentration. Research efforts to achieve chiral specific growth are ongoing The use of carbon nanotubes (CNTs) in photovoltaics could have significant ramifications on the commercial solar cell market. Three interrelated research directions within t...

Solution‐Processed Chemically Non‐Destructive Filter Transfer of Carbon‐Nanotube Thin Films onto Arbitrary Materials

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attention based on their unique properties such as flexibility, electrical and thermal conductivities, and enhanced p-type [6,9] and modified n-type [10] semiconductor characters. [2,11,12] In low-temperature solution-processable device technologies, such convenient and low energy-consuming processes have prompted exhaustive wide-field research. [13][14][15] Environmentally friendly aqueous dispersion solutions of single-walled CNTs (SWNTs) are industrially applicable; however, we suffer from dispersant molecules seriously insulating electrical communication on solution-processed SWNT film networks.

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Recent Advances in Structure Separation of Single‐Wall Carbon Nanotubes and Their Application in Optics, Electronics, and Optoelectronics

“…[345] More descriptions on SWCNT-based light detection devices can be found in recent review manuscripts. [27,263] The NIR emission wavelengths of semiconducting SWCNTs are located exactly within the biological transparency window and have strong penetration abilities in biological compounds and tissues. [346][347][348] Separated single-chirality SWCNTs have a promising future in bioimaging, which plays a pivotal role in the field of biomedicine and life sciences.…”

“…Most recently, Flavel et al estimated the cost of (6, 5) SWCNTs separated by polymer wrapping and ATP methods based on the prices of raw SWCNTs, dispersants (polymers or surfactant), solvents and additives from commercial chemical suppliers. [ 263 ] The estimated cost of (6, 5) SWCNTs produced by the polymer wrapping method under laboratory conditions is as high as €36 000–73 000 g −1 , which is much higher than that by ATP (€8300–13 000 g −1 ). [ 263 ] The separation cost of SWCNTs by gel chromatography is similar to that of ATP.…”

Role of carbon nanotubes as an acceptor to enhance the photovoltaic performances of organic solar cells based on π ‐conjugated thiophene as a donor materials

“…Hence, in recent years, researchers have been attracted to the use of blends of π ‐conjugated polymers and carbon nanotubes (CNTs) in these solar cells due to avoiding carrier recombination, and indicate that an efficient quenching of the excitons takes place at these interfaces 22‐25 . In addition, due to their extremely high conductivity, SWNTs may yield higher mobilities and form more conductive percolation networks than fullerenes.…”