Influence of Solid-State Packing of Dipolar Merocyanine Dyes on Transistor and Solar Cell Performances

A series of nine dipolar merocyanine
dyes has been studied as organic
semiconductors in transistors and solar cells. These dyes exhibited
single-crystal packing motifs with different dimensional ordering,
which can be correlated to the performance of the studied devices.
Hereby, the long-range ordering of the dyes in staircase-like slipped
stacks with J-type excitonic coupling favors charge
transport and improves solar cell performance. The different morphologies
of transistor thin films and solar cell active layers were investigated
by UV–vis, AFM, and XRD experiments. Selenium-containing donor–acceptor
(D–A) dimethine dye 4 showed the highest hole
mobility of 0.08 cm2 V–1 s–1. BHJ solar cells based on dye 4 were optimized by taking
advantage of the high crystallinity of the donor material and afforded
a PCE of up to 6.2%.