Cyclopentadithiophenes(389-58-2) and its polymers applications as electron donor materials for organic solar cells

 Organic electronics has been rapidly developing during the last decade. Conjugated polymers form one of the most important groups of organic semiconductors. Depending on the molecular structure,conjugated polymers demonstrate semiconducting properties of both p- and n-types, which makes them promising materials for organic solar cells, photodetectors, field-effect transistors and light-emitting diodes [1-6]. The use of the soluble polymer-based materials allows for the manufacture of flexible, lightweight and cheap organic solar cells. The active layer of such solar cells is represented by a composite of a conjugated polymer with appropriate n-type semiconductor material, which is typically some soluble fullerene derivative. The efficiency of the best organic solar batteries reaches 6-8% nowadays [7-12]. It might be possible to reach higher efficiencies by using new polymer-based materials with improved properties [13]. However, the guidelines for the design of well-performing conjugated polymers are not established up to date because of the complex morphological behaviour of the fullerene/polymer

composites [14]. A family of conjugated poly(4,4-dialkylcyclopentadithiophene)-2,6-diyls (PACPDTs) bearing alkyl

side chains of different lengths might be considered as good model polymer system for investigation in bulk heterojunction organic solar cells in combination with fullerene derivatives. PACPDTs have superior optical properties compared to the poly(3-alkylthiophenes) (PATs) that potentially allow for the generation of higher current densities and overall power conversion efficiencies in solar cells using these

materials [ 15 - 16 ]. Many conjugated copolymers comprising cyclopentadithiophene units were synthesized and investigated in organic solar cells [17-22]. However, PACPDTs homopolymers were not investigated up to our best knowledge. In this work we performed a systematic investigation of PACPDTs homopolymers bearing side chains varied from hexyl to decyl as electron donor materials in organic solar cells.