Strongly enhanced efficiency of polymer solar cells through unzipped SWNT hybridization in the hole transport layer

Abstract

<p>Single-walled carbon nanotubes (SWNTs) have good conductivity, but their size can't match the heterojunction nanostructure in polymer solar cells (PSCs).</p>

Recent Advances in Hole-Transporting Layers for Organic Solar Cells

“…Single-walled carbon nanotubes (SWCNTs) are promising p -type transparent conductors owing to their superior hole mobility, conductivity, and facile tuning of the WF by doping method [ 253 ]. A highly-conductive composite of unzipped single-walled carbon nanotubes (u-SWNTs) and PEDOT:PSS was synthesized by a facile solution processing method as reported by Zhang et al (see Figure 13 b) [ 254 ]. The hybrid PEDOT:PSS doped with u-SWNTs decreased the surface roughness.…”

“…( b ) Schematic representation of u-SWNTs and u-MWNTs synthesis, ( c ) EQE of u-SWNTs, SWNTs, and PEDOT:PSS, and ( d ) J-V curves of the OSCs with u-SWNTs HTLs. Adapted with permission from [ 254 ]. Copyright 2020, Royal Society of Chemistry.…”

Recent Applications of Carbon Nanotubes in Organic Solar Cells

“…Several HTL materials, including the p-type semiconducting polymer PEDOT:PSS; inorganic metal oxides, e.g., nickel oxide (NiO), MoO 3 , and vanadium pentoxide (V 2 O 5 ); and carbon-based materials, e.g., CNTs and graphene, have been recently employed in OSCs ( Mbuyise et al, 2017 ; Singh et al, 2017 ; Hilal and Han, 2019 ; Mohammad et al, 2019 ; Rafique et al, 2019 ; Li J. et al, 2020 ). Among these, PEDOT:PSS is the most commonly used HTL due to its high optical transmittance in the visible region, which permits more light to pass to the active layer for effective exciton generation, and its suitable work function, which aligns the energy levels between the active layer and anode for efficient hole extraction ( Dang et al, 2018 ; Zhang W. et al, 2020 ). In addition, PEDOT:PSS is compatible with low-cost solution processing and has a smooth surface morphology, which moderates the surface roughness of the anode; hence, reducing the likelihood of undesirable effects, such as charge carrier traps and short-circuits, and thereby suppressing charge carrier recombination and leakage current ( Ricciardulli et al, 2017 ; Sorkhishams et al, 2019 ).…”

“…Consequently, devices with the PEDOT:PSS/acid-treated SWCNTs:P3HT HTL exhibited higher J sc ; hence, a higher PCE of 2.52%, which outperformed devices based on P3HT/PEDOT:PSS HTLs that had a PCE of 2.48%. A significant increase in hole transport efficiency and electrical conductivity has also been observed after incorporating unzipped SWCNTs (uSWCNTs) into PEDOT:PSS to form a composite HTL of BHJ-OSCs ( Zhang W. et al, 2020 ). This, in turn, increased the J sc and FF, resulting in devices with a higher PCE of 14.60% when compared with 5.93 and 13.72% for the pristine uSWCNTs and PEDOT:PSS devices, respectively.…”

“…The photovoltaic parameters of OSCs with CNT-based HTLs, discussed in this work, are summarized in Table 3 . Among these, the best PCE of 14.60% was obtained in more stable devices with uSWCNTs/PEDOT:PSS HTLs ( Zhang W. et al, 2020 ). Hence, as a future research direction, the integration of CNTs with the conventional PEDOT:PSS HTL is envisaged to result in devices with excellent performance and stability, which is a significant step towards commercialization.…”