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 <i>J</i>-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 <b>4</b> showed the highest hole mobility of 0.08 cm² V^–1 s^–1. BHJ solar cells based on dye <b>4</b> were optimized by taking advantage of the high crystallinity of the donor material and afforded a PCE of up to 6.2%