High molecular weight polymeric acceptors based on semi-perfluoroalkylated perylene diimides for pseudo-planar heterojunction all-polymer organic solar cells

Abstract

In this study bulk heterojunction (BHJ) and pseudo-planar heterojunction (PPHJ) organic solar cells (OSCs) were prepared and studied with perylene diimides (PDIs)-based polymeric acceptors P(4CF8CH-PDI-TT) and P(20CH-PDI-TT). The PDI polymers were used in PPHJ all-polymer solar cells for the first time. Its high molecular weight (Mn of 94.8 kDa), high mobility (μe of 8.40 × 10−3 cm2 V−1 s−1), and excellent solubility make semi-perfluoroalkylated polymer P (4CF8CH-PDI-TT) well polymeric acceptor for PPHJ OSCs. A series of measurements including photoluminescence quenching, dependence of light intensity, carrier mobility, atomic force microscopy, transmission electron microscopy, grazing-incidence wide-angle X-ray scattering, and depth analysis X-ray photoelectron spectroscopy were carried out. The results show that PPHJ devices prepared by the layer-by-layer spin-coating method have better charge transport, higher and more balanced carrier mobility, less exciton recombination loss, and more favorable film morphology than BHJ devices. Consequently, the PPHJ OSCs based on P(4CF8CH-PDI-TT) and P(20CH-PDI-TT) gave power conversion efficiencies (PCE) of 3.43% and 3.15%, respectively, which are higher than 1.71% and 1.10% of BHJ OSCs. It demonstrates that semi-perfluoroalkylated strategy is effective for the construction of high-performance polymeric semiconductors with the PDI block.