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

Abstract

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. Rinzler et al. overcame the drawback by a breakthrough filter-transfer method using a mixed cellulose ester (MCE) membrane. The filtrated ultra-thin SWNT films were transferred onto substrates by the dissolution removal of MCE (Figure 1, Method A). [16] Jin et al. reported that a floating method of a similarly filtrated SWNT thin film apart from MCE, and the as-floated SWNT film was picked up on a substrate (Method B). [17] See-through perovskite (PVK) solar cells have been successfully prepared using top-contact SWNT thin films [18,19] by a dry filter-transfer method using MCE membranes reported by Kauppinen et al. [20] Simply structured crystalline Si-SWNT heterojunction solar cells have been prepared by the solution-processed [21][22][23][24][25][26][27][28] and dry filter-transfer [29][30][31][32] methods with increasing photo-conversion efficiencies up to ≥17%. [25,31,33,34] See-through solar cells are indispensable for state-of-the-art tandem devices combined with crystalline Si solar cells driven by visible and near IR lights. [35,36] The stability of CNTs against chemical corrosion is a fascinating feature as a top-contact electrode on the PVK layers. The high-conductivity p-type semiconductor character of CNTs with the ≈5 eV work function realizes hole-transport layer-free PVK solar cells. [2,[37][38][39] Therefore, the discovery of a convenient solution-processable technology for preparing top-contact thin films of SWNTs using their aqueous dispersion solutions is key to achieving all solution-processed photovoltaic cells that exclude evaporated metal electrodes and expensive p-type organic semiconductors; however, PVK layers are sensitively decomposed by water, some hydrophilic solvents, and some dissolved chemicals. Furthermore, solution-processable p-type doping technologies of SWNT thin films are crucial Filter-transfer methods of single-walled carbon-nanotube (SWNT) thin films have been widely employed to fabricate state-of-the-art electronics and photonics devices with highly transparent and conductive electrodes; however, a challenge remains for all solution-processable technologies to overcome substrates' destruction due to their solvent incompatibility. Here, an advanced method of transferring SWNT thin films onto arbitrary material substrates by adopting chemically stable and flexible polytetrafluoroethylene (PTFE) membranes is reported. Filtrated SWNT thin films on PTFE membranes (PTFE@SWNTs) pres...

Low-Temperature Edge-Fusing Phenomenon of Silver Microplates and Solution-Processed Low-Resistivity Top-Contact Electrodes

“…An aqueous dispersion solution of single-walled carbon nanotubes (Meijo Nanocarbon EC1.5-P) was prepared as described in our previous reports. 53 The AgMLs and AgML−SWNT mixtures were filtered through hydrophobic PTFE membrane filters (PORE-FLON HP-010-30, pore size = 100 nm) purchased from Sumitomo Electric. Slide glasses (Matsunami Glass S1127) were divided into glass plates (2.5 × 2.5 cm 2 ) and washed in a sonication bath with a cleaning liquid (AS ONE SDNU-N4), followed by a sequence of two water washings, two acetone washings, and two isopropanol washings.…”

“…As described in our previous report, 53 a PVK layer (CH 3 NH 3 PbI 3 ) was directly prepared on a glass plate. An aqueous dispersion solution of SWNTs (1.1 μg mL −1 , 5.0 mL) was passed through a PTFE membrane filter and washed twice with water (Figure S1a).…”

“…262853 Therefore, the AgML film filtered through a PTFE membrane filter, PTFE@ AgML(purified), was immersed in a toluene bath to displace the wet solvent from ethanol to toluene. 53 Although the AgML film was successfully transferred from ethanol-wetted PTFE@ AgML(purified) to a glass plate (Figure 4b), the film remained on the PTFE membrane when transferred from toluene-wetted PTFE@AgML(purified) via the same filter-transfer process. Previously, we reported the complete transfer of low-density semitransparent SWNT thin films onto arbitrary substrate materials by a filter-transfer method similar to that shown in Figure 2c.…”

“…In 2021, we reported a solution-processed filter-transfer method for transferring single-walled CNT (SWNT) films onto various substrates. Our method overcomes the following concerns: 53 (i) excess additives such as surface-protecting molecules and surfactants, which prevent electrical contact among the SWNTs; (ii) decomposition of the sublayers by dispersion solvents and/or additives; and (iii) the external pressure of film adhesion, which can destroy the fragile sublayers and/or push SWNTs into the sublayers.…”

“…As the ethanol evaporates, the AgML film spontaneously transfers to the glass plate, leaving the membrane behind. If necessary, the wet ethanol solvent can be replaced by different solvents by immersing the ethanolwetted PTFE@AgML in a solvent bath 53.…”