The effect of branched versus linear alkyl side chains on the bulk heterojunction photovoltaic performance of small molecules containing both benzodithiophene and thienopyrroledione

Abstract

To evaluate the effect of side chain characteristics on the photovoltaic performance of small molecules containing both benzodithiophene (BDT) and thienopyrroledione (TPD), we designed and synthesized two such molecules, one containing a branched 2-ethylhexyl (2EH) side chain on the BDT unit (BDTEH-TTPD) and the other containing a linear n-octyl (C8) side chain on the BDT unit (BDTO-TTP). The optical and electrochemical properties and crystalline structures of these molecules were examined. Compared to BDTO-TTPD, BDTEH-TTPD, showed stronger light absorption, longer-range ordering and shorter π-π stacking distances between backbones. As a result, the power conversion efficiency of a bulk heterojunction solar cell based on BDTEH-TTPD (2.40%) was substantially higher than that of the BDTO-TTPD device (1.12%).

The Major Influences of Substituent Size and Position of 3,4‐Propylenedioxythiophene on the Formation of Highly Hydrophobic Nanofibers

“…Obtaining highly hydrophobic properties with nanofibers can be explained by the Wenzel [31] and Cassie-Baxter theories [33] that are often used to predict the possibility of obtaining superhydrophobic properties. A water droplet in the Wenzel state follows the surface roughness.…”

Efficient solution processed D1-A-D2-A-D1 small molecules bulk heterojunction solar cells based on alkoxy triphenylamine and benzo[1,2-b:4,5-b′]thiophene units

“…1 and corresponding optical data are summarized in Table 1. Both VC96 and VC97 show two absorption bands in the wavelength range of 300-400 nm, which can be ascribed to the pp ⁄ transition of the p-conjugation system [43], and another strong absorption band from wavelength region 430-650 nm (maximum absorption peak for both VC96 and VC97 538 nm) may be ascribed to the ICT transition [44] from the trithiophene moieties to the benzothiadiazole moieties, as discussed in the theoretical section. In thin film, VC97 displays a red shift k max at 568 nm with a maximal absorption and also showed a vibronic shoulder around 626 nm.…”

A Review on the Thieno [2,3-c]pyrrole-4,6-dione-based small molecules for Organic Photovoltaic Cells

“…Two TPD based small molecule of 9a and 9b with A-D-A framework with benzodithiophene (BDT) as core unit were reported by Kim et al (2014). 9a contains a branched 2-ethylhexyl (2EH) side chain while 9b contains a linear noctyl side chain on the BDT unit [34] .…”

“…9a contains a branched 2-ethylhexyl (2EH) side chain while 9b contains a linear noctyl side chain on the BDT unit [34] . 9a blends with PC71BM (1:4, w/w) shows PCE of 2.40% compared to the 9a with PC61BM at the same ratio with PCE only 1.71%.…”