Color Tunable π-Conjugated Polymers for Solar-Cell Applications: Engineering of Bandgap, Interface, and Charge Transport Properties

While power-conversion efficiency is an important metric for energy harvesting in polymer solar cells (PSCs), the aesthetics of the devices is also important in some special applications. To fabricate aesthetically pleasing PSCs, we have designed and synthesized a series of blue, blue-green, and green π -conjugated copolymers (P1, P2 , and P3) comprising electron-rich 3,4-dioxythiophenes (DOTs) and electron-deficient 2,1,3-benzothiadiazole (BTD) as the donor-acceptor units. In this paper, we review the optical, electrochemical, morphological, and charge transport properties of these DOT-BTD copolymers, and demonstrate how the color of the polymers and the solar-cell performance can be controlled by the molecular design of the polymers. Using as an anode interlayer, the maximum Air-mass (AM) 1.5 power-conversion efficiency of [6,6]-phenyl-C71 butyric acid methyl ester (PC70BM) blend solar cells based on these polymers is 3.2%.