A Solution-Processable Dithienyldiketopyrrolopyrrole Dye Molecule with Acetylene as a π-Linkage for Organic Solar Cells

Unravelling the Self-Assembly of Diketopyrrolopyrrole-Based Photovoltaic Molecules

The nanostructure of bulk heterojunction in an organic solar cell dominating the electron transport process plays an important role in improving the device efficiency. However, there is still a great need for further understanding the local nanostructures from the viewpoint of molecular design because of the complex alignment in the solid film. In this work, four kinds of photovoltaic materials containing a diketopyrrolopyrrole (DPP) unit combined with other different building blocks were selected and their self-assembled structures on a solid surface were studied by scanning tunneling microscopy technique in combination with theory calculations. The results reveal these DPP-based photovoltaic molecules self-assembled into different nanostructures, which strongly depend on the chemical structure, in particular the backbones and alkyl side chains. The planarities of backbones are affected both by molecule-substrate interaction and steric hindrance induced by the substituted thiophene or benzo[ b]thiophene units on DPP and porphyrin building blocks. The substituted branched alkyl side chains are out of the plane, which are influenced by the alignments of molecular backbones. In addition, the solution concentration also shows a large effect on the self-assembled nanostructures. This systematic research on the self-assembled structures of DPP-based semiconductors on a surface would provide guidance for designing materials and controlling the morphology of a donor/acceptor heterojunction system.

Rise of Conjugated Poly-ynes and Poly(Metalla-ynes): From Design Through Synthesis to Structure-Property Relationships and Applications

Conjugated poly-ynes and poly(metalla-ynes) constitute an important class of new materials with potential application in various domains of science. The key factors responsible for the diverse usage of these materials is their intriguing and tunable chemical and photophysical properties. This review highlights fascinating advances made in the field of conjugated organic poly-ynes and poly(metalla-ynes) incorporating group 4-11 metals. This includes several important aspects of conjugated poly-ynes viz. synthetic protocols, bonding, electronic structure, nature of luminescence, structure-property relationships, diverse applications, and concluding remarks. Furthermore, we delineated the future directions and challenges in this particular area of research.

Design of Diketopyrrolopyrrole (DPP)-Based Small Molecules for Organic-Solar-Cell Applications

After the first report in 2008, diketopyrrolopyrrole (DPP)-based small-molecule photovoltaic materials have been intensively explored. The power conversion efficiencies (PCEs) for the DPP-based small-molecule donors have been improved up to 8%. Furthermore, through judicious structure modification, DPP-based small molecules can also be converted into electron-acceptor materials, and, recently, some exciting progress has been achieved. The development of DPP-based photovoltaic small molecules is summarized here, and the photovoltaic performance is discussed in relation to structural modifications, such as the variations of donor-acceptor building blocks, alkyl substitutions, and the type of conjugated bridges, as well as end-capped groups. It is expected that the discussion will provide a guideline in the exploration of novel and promising DPP-containing photovoltaic small molecules.