Effects of oligothiophene π-bridge length on physical and photovoltaic properties of star-shaped molecules for bulk heterojunction solar cells

Abstract

and fill factor (FF). The study demonstrates that such an approach can represent an interesting tool for the effective modulation of the photovoltaic properties of the organic solar cells (OSCs) at a moderate cost.

Star-shaped D–π–A oligothiophenes with a tris(2-methoxyphenyl)amine core and alkyldicyanovinyl groups: synthesis and physical and photovoltaic properties

“…8c) and also consistent with our previous results. 16,35 In addition, the slightly higher V oc values (see Fig. 8c) for N(Ph-OMe-2T-DCV-Me) 3 and N(Ph-OMe-3T-DCV-Hex) 3 as compared to N(Ph-OMe-2T-DCV) 3 and N(Ph-OMe-3T-DCV-Et) 3 may be explained by the presence of longer terminal alkyl groups for the former, leading to a weakening of the intermolecular interactions between the donor and the acceptor moieties.…”

“…Synthesis of star-shaped oligomers with m-TPA and alkyl-DCV groups, N(Ph-OMe-2T-DCV) 3 , N(Ph-OMe-2T-DCV-Me) 3 , 35 N(Ph-OMe-3T-DCV-Et) 3 , and N(Ph-OMe-3T-DCV-Hex) 3 , was carried out using our recently developed approach for their analogs with the TPA core. 15,16 The synthetic routes outlined in Scheme 2 include several key reaction stages: preparation of the initial aldehyde or ketones (Schemes 2a and b), synthesis of an organoboron derivative of bi-or terthiophene precursors (Scheme 2c), and preparation of star-shaped precursors with protective groups followed by the deprotection reaction and substitution of carbonyl functions by DCV groups (Scheme 2d).…”

“…34 In this work we report on the synthesis and a comprehensive study of a series of four D-p-A oligomers having the tris-(2-methoxyphenyl)amine (m-TPA) core as a donor, either alkyl-DCV or DCV as acceptor units, and either bi-or terthiophene as p-bridges (Scheme 1). A comparison of properties of these four molecules with those of their full analogs with a TPA core [15][16][17]35 reveals the benefits and drawbacks of this chemical design strategy. Furthermore, variation of the p-bridge and the alkyl chain length as well as the type of substituent at the DCV group allows elucidating the structure-property relationships in this series of star-shaped molecules systematically.…”

Organic solar cells based on acceptor-functionalized diketopyrrolopyrrole derivatives

“…It has been suggested that fullerene acceptors in the blend films distort the molecular packing of the donor polymer/small molecule and, thereby, decrease the effective conjugation length. 24,34 This effect would be larger for higher fullerene concentrations.…”

4H-1,2,6-Thiadiazin-4-one-containing small molecule donors and additive effects on their performance in solution-processed organic solar cells

“…17 Devices employing solution-processed small molecules as both donor and acceptor components gave device efficiencies of $3%, 18 which is similar to the average device performance of the widely studied and extensively optimized polymer : fullerene P3HT : PC60BM system. 19 As a result of this progress, a wide variety of new small molecules for solutionprocessed organic photovoltaics are being prepared, [20][21][22][23][24] including efficient donor-acceptor-donor (D-A-D) systems. 25 A recent electrochemical study of non-oxidised 4H-1,2,6-thiadiazines indicated electron affinities (LUMO energy values) of À3.25 to À3.66 eV with reversible oxidations and reductions.…”