3D nanoscale ordered architectures in thin films for organic electronics

Abstract

Order in molecular thin films is of fundamental importance to gain and exploit a series of properties in nanotechnology. In this contest, engineering 2D supramolecular and molecular superstructures is of particular interest. They offer great possibilities for several applications whose achievement also allows for new theoretical approaches and nanoscale laws [1]. A natural extension of 2D nanopatterning concerns the attainment of a 3D nanoscale control in molecular films [2]. This question is complex to challenge and it is of ultimate importance in emerging fields like organic and hybrid photovoltaics, organic thin film transistors and sensors as well as plastic electronics. For example, the development of nanostructured bi-continuous bulk heterojunctions (BHJs) is an important advancement leading to improved photovoltaic power conversion efficiency (PCE) with respect to planar heterojunctions. In a previous work we obtained PCE of about 3 % employing the BHJ concept for all-polymer solar cells [3,4]. In this study, we show an innovative approach for the construction of 3D ordered and modulable BHJs architectures of two different polymer blends: Poly(3-hexylthiophene-2,5-diyl):Phenyl-C61-butyric acid methyl ester (P3HT:PCBM) and Poly(3-hexylthiophene-2,5-diyl):Poly(9,9-dioctylfluorene-alt-benzothiadiazole) (P3HT:F8BT). When exposed to light irradiation, these blends give rise to two different mechanism of electro-optical interaction: Charge Transfer (CT) and the Forster Reso