A single cis-2 regioisomer of ethylene-tethered indene dimer–fullerene adduct as an electron-acceptor in polymer solar cells

Abstract

A pure cis-2 isomer of indene dimer-based fullerene bis-adduct has been synthesized, isolated and applied to bulk heterojunction solar cells for the first time. The device based on the cis-2 isomer and poly(3-hexylthiophene) exhibited a power conversion efficiency of 2.8%, which is higher than those of the reference devices.

Synthesis and Isolation of cis-2 Regiospecific Ethylene-Tethered Indene Dimer–[70]Fullerene Adduct for Polymer Solar Cell Applications

“…12,13,43 The 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 (Table 2 and Figure S8a). 19 (Table 2) are lower than those of cis-2-[60]BIEC, bis-[60]BIEC, and mono-[60]BIEC (3.5 × 10 -5 , 2.5 × 10 -5 , and 2.7 × 10 -5 cm 2 V -1 s -1 , respectively). 19 The lower symmetrical fullerene cage structure of C 70 than C 60 would hinder the formation of closely packed structures of the C 70 derivatives, as suggested from the packing structure of cis-2-[70]BIEC ( Figure 3 and Figure S5).…”

“…The differences in the theoretical LUMO levels between the fullerene derivatives largely agree with those obtained from the electrochemical measurements (Table 1). 19 The HOMO level of cis-2- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 adducts are low and high, respectively, compared to those of the C 60 -BIE adducts. As regards to the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The thermal stability of cis-2-[70]BIEC was evaluated by thermogravimetric analysis (TGA, …”

“…The synthesis and isolation of the BIE-C 70 adducts have been conducted, as described for the BIE-C 60 adducts (Scheme 1). 19 Diels-Alder reaction between BIE and C 70 in refluxing product in an overall yield of 32% based on the amount of reacted C 70 . In addition, the second fraction was also subjected to the HPLC purification ( Figure S1b).…”

“…In 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 the same hexagon, the structure is denoted as the cis-2 isomer of C 70 bis-adducts. Two methylene bridges of the indene addends are protruding on the same side as seen in cis-2-[60]BIEC, 19 properties of the BIE-C 70 adducts were evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements ( Figure 4). The first (E 1 ), second (E 2 ), and third (E 3 ) reduction potentials determined from the DPV peaks 18 are listed in Table 1 To get more insight into the electronic structures of the fullerene derivatives, we performed density functional theory (DFT) calculations using RB3LYP/6-31G (d) model.…”

“…As is the case with BIE-C 60 adducts, 19 the superior photovoltaic performance of the cis-2 bis-adduct was exemplified in the C 70 -based fullerene derivatives (Figure 6a and Table 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 (2.2%) and even a prevalent high-performance C 70 mono-adduct, (Table 1). A similar phenomenon has been observed with other Diels-Alder fullerene adducts, in which the cofacial π-orbital interactions between the fullerene orbitals and the aromatic addend ring decrease the electron affinity and thereby increase the LUMO energy level.…”