Polymers/Soft Matter Prospective Article Functional semiconductors targeting copolymer architectures and hybrid nanostructures Joannis K. Kallitsis, Department of Chemistry, University of Patras, Rio-Patras, Greece; Foundation for Research and Technology Hellas, Institute of Chemical Engineering Sciences (FORTH-ICE-HT), Patras, Greece Charalampos Anastasopoulos, Department of Chemistry, University of Patras, Rio-Patras, Greece Aikaterini K. Andreopoulou, Department of Chemistry, University of Patras, Rio-Patras, Greece; Foundation for Research and Technology Hellas, Institute of Chemical Engineering Sciences (FORTH-ICE-HT), Patras, Greece Address all correspondence to Joannis K. Kallitsis at j.kallitsis@upatras.gr (Received 26 March 2015; accepted 10 June 2015) Abstract The introduction of functional units onto semiconducting polymers either as side chains or at the α- and ω-ends of polymeric chains is the method of choice in order to impose additional functions to the final semiconducting materials when aiming specific applications. Moreover, the functional- ization approach provides a route to further complex macromolecular architectures as well as the generation of hybrid materials through the covalent attachment of the semiconductor to carbon nanostructures or to inorganic nanoparticles. Via this prospective an outline over functionalized and hybrid semiconducting polymers is provided along with possible paths of future research toward functional and hybrid semiconductors. Introduction The unique properties of organic conducting polymers were first discovered by Heeger, Shirakawa, and MacDiarmid back in the 1970s. This discovery was the genesis of an enormous amount of work in the area of organic electronics and was final- ly honored with the Nobel Prize in Chemistry in 2000. [1] Conjugated semiconducting polymers offer broad applications in the field of molecular electronics. Perhaps the most attractive research area in polymers nowadays is the development of novel semiconducting polymers for organic photovoltaics (OPVs), organic light emitting diodes (OLEDs), organic thin film transistors (OTFTs), sensors, etc. [2] Their properties mod- ulation via precise control of the molecular structure has populated a vast number of publications, patents, and further technological breakthroughs in the past 2–3 decades. Conjugated polymers and oligomers offer the unique capability of tuning the final semiconducting materials’ properties via a cor- rect choice of the chemical structure and the synthetic methodol- ogy, the variation of conjugation length, and the substitution pattern of side groups. Besides their inherent function of charge carrier generation and transport and their nanomorphology based on π–π-stacking interactions, the alteration of their exact chemi- cal structure, and the introduction of side or main chain function- alities, meaning moieties that can lead to further reactions and/or interactions, greatly expand their properties and potentiality. Net, unsubstituted conjugated polymers such as poly (p-phenylene), poly(p-phenylene vinylene), etc., suffer from low to negligible solubilities due to extended π-stacking prohibiting thus, their processing from solution to thin films. In the vast number of cases, the semiconducting macromolecular chains are decorated with alkyl, alkoxyl, branched, or even dendritic side units which serve a dual scope: to impose solubility and processability to the final semiconductor as well as to enhance nanophase ordering and crystallization in the thin film which are essential for charge transport in most of the organic electronic devices. On the other hand, and since their discovery back in the early 1990s, fullerenes and carbon nanotubes (CNTs) have at- tracted scientific interest as promising materials for novel appli- cations. The realization of their electronic properties opened new possibilities for technological applications such as in or- ganic electronics. Almost 20 years after the realization of the bulk heterojunction photovoltaics (BHJ PVs), based on the combination of polymeric conjugated electron donors and ful- lerene derivatives as electron acceptors, the efficiency of these systems has exceeded 10% boosting their perspective for com- mercialization. Certain figures of BHJ PVs such as reduced cost, mechanical flexibility, impact resistance, optical transpar- ency, large area coverage, and printability are their most prom- inent advantages over the competing silicon-based PV technologies. The active layer of a typical organic PV cell is composed of a polymeric semiconductor, as the electron donor, blended with a fullerene derivative, as the electron ac- ceptor. The known semiconducting conjugated polymers poly (1,4-phenylene-vinylene)s (PPVs) and poly(3-hexylthiophene) (P3HT) were initially used as the electron donors, that after light absorption generate excitons which dissociate to provide electrons to a neighboring electron-accepting phase. Efficient matching of the energy levels of the electron donor and the MRS Communications (2015), 5, 365–382 © Materials Research Society, 2015 doi:10.1557/mrc.2015.42 MRS COMMUNICATIONS • VOLUME 5 • ISSUE 3 • www.mrs.org/mrc ▪ 365