Effect of Photocrosslinking of D‐A Thiophene Copolymers on the Performance of Single‐Material Solar Cells

Abstract

Side‐chain C60‐fullerene functionalized alkylthiophene copolymers with different regioregularity and fullerene content are successfully synthesized using a simple and straightforward post‐polymerization functionalization procedure based on a Grignard coupling reaction. The products are employed as single materials in photoactive layers of organic photovoltaic solar cells. The use of double‐cable polymers allows an enhanced control on the nanomorphology of the active blend, reducing the phase‐segregation phenomena as well as the macroscale separation between the electron acceptor and donor components. With the insertion of a thin layer of gold nanoparticles between buffer and active layer of the cells, a conversion efficiency of 5.68% is obtained. Moreover, an increased stability over time is achieved when the copolymers are photocrosslinked immediately after the annealing procedure, leading to acceptable efficiencies even after 80 h of accelerated ageing, a key feature for widespread applicability of the prepared devices.

Influence of the Active Layer Structure on the Photovoltaic Performance of Water-Soluble Polythiophene-Based Solar Cells

“…For this purpose, the double-cable copolymer P[(T6buP + )- co -(T6F)] was prepared to combine the excellent solubility in water of phosphine-substituted polythiophene-based materials with the high electron affinity of fullerene derivatives. In particular, starting from the previously synthesized PT6Br, a non-ionic double-cable copolymeric precursor P[(T6Br)- co -(T6F)] with 7% fullerene content was prepared, according to the procedure reported in the literature [ 5 ] (p. 2). The obtained product was then post-functionalized with tributylphosphine using the same reaction conditions as the preparation of the homopolymer PT6buP + , but with a reduced reaction time (from 24 to 5 h), in order to prevent any loss of C 60 from the side chains ( Scheme 2 ).…”

“…The regioregular homopolymeric precursor PT6Br was prepared starting from 2,5-dibromo-3-(6-bromohexyl)thiophene (2, [5,20] (p. 2,3); while the post-polymerization functionalization of PT6Br gave the corresponding water-soluble homopolymer PT6buP + , the water-soluble electron acceptor fullerene derivative (C60-Ser) was obtained from the properly functionalized serinol, according to the procedure shown in Scheme 1. Scheme 1.…”

“…In order to obtain optimized and enhanced structures, a possible technique may be the chemical modification of the polymeric structure: a double-cable material is obtained by linking the EA group to the end of the side chains linked to the polyconjugated backbone [ 4 ]. However, even though important improvements such as a better morphology of the photoactive layer and a more efficient energy conversion of final devices have been obtained, earlier studies [ 5 ] have proved that the content of the EA group, e.g., fullerene, should be appropriate to obtain a good solubility in common organic solvents and at the same time an efficient collection of electrons during charge separation. Moreover, it should be recognized that the production of OPVs very often requires the consumption of large amounts of chlorinated and/or aromatic organic toxic solvents.…”

Single-Component Organic Solar Cells with Competitive Performance

“…85 Later on, reported by the same group, based on the same structure but with Br-end-capped groups for photo-crosslinking, a similar double-cable polymer P14b (also resembling P13) exhibited an efficiency of 5.68% (FF, 0.67; EQE max , 0.68), which is remarkably high for a P3HT-PCBM type system. 86 SCOSCs based on P14 are the only ones showing efficiencies higher than 5% employing fullerene as acceptors; the others are all based on NFAs.…”

EQCM Analysis of the Insertion Phenomena in a n-Doped Poly-Alkyl-Terthiophene With Regioregular Pattern of Substitution

“…Polythiophenes (PTs) are heterocyclic polymers with an extended area of electronic delocalization ( Brédas et al, 2016 ), which possess high chemical and physical stability ( Tourillon and Skotheim, 1986 ). By virtue of these properties, PTs are successfully employed as active materials in many advanced applications, e.g., photovoltaic cells ( Marinelli et al, 2020a ; Lanzi et al, 2020 ; Lanzi et al, 2018 ; Kippelen et al, 2016 ), sensors ( Wang et al, 2017 ; Chan et al, 2017a ; Guiseppi-Elie et al, 1998 ), and electroluminescent devices ( Kerfoot et al, 2020 ; Kameta and Shimizu, 2020 ; Menke et al, 2016 ), among others ( Lodola et al, 2019 ; Barbarella and Di Maria, 2015 ; Di Maria et al, 2014 ; Zessin et al, 2017 ; Carreon et al, 2014 ; Chaudhary et al, 2019 ; da Rocha Rodrigues et al, 2020 ; Jung et al, 1998 ; Angiolini et al, 2013 ; Sheehan et al, 2015 ; Zheng et al, 2016 ). PTs are also studied in the ambits of nonlinear optics ( Hartmann et al, 2001 ; Jahja and Bubeck, 2010 ; Persoons et al, 2016 ), photonics ( Portone et al, 2019 ; Cornil et al, 1999 ), and organic electronics ( Hsieh et al, 2016 ; Kanibolotsky et al, 2015 ; Lee et al, 2016 ) due to the high polarizability and mobility of the π-electrons present in large concentrations ( Xie et al, 2016 ; Kossmehl and Skotheim, 1986 ).…”