SOLiCOAPs · Self-Organising Liquid-Crystalline OligoAnilines for Photovoltaic Applications

Self-organising liquid-crystalline oligoanilines for photovoltaic applications

This project aimed to design, synthesize and characterize self-organising liquid-crystalline oligoanilines for photovoltaic applications. Recently, self-assembled liquid crystals with semiconducting properties are being exploited as organic semiconductors [1]. In self-assembled liquid-crystalline (LC) semiconducting materials, p-stacking of aromatic molecules is enhanced and the electronic coupling of adjacent molecules is increased, which can potentially lead to very high charge carrier mobilities. Therefore, LC organic semiconductors are more promising than amorphous organic semiconductors, which offer potential applications in a variety of electronic devices [2]. In this project we designed and synthesized novel LC tetra(aniline) (TANI) derivatives by introducing a alkoxybenzene chains onto the terminal phenyl unit (Figure 1). The prepared LC TANIs were blended with PC60BM and IC60BA for photovoltaic (PV) studies. The synthesised TANIs as well as photoactive blend materials were characterized by physical and chemical characterization methods. The main results achieved within this project are: • The synthesis and characterisation of the first ever LC TANI in the half-oxidised EB state (with two hexyloxy side chains at the meta and para positions). • The photoluminescence (PL) quenching of well-known C60 electron-acceptor species by TANI EB derivatives was observed in the range from 93-100% (Figure 2), indicating promising properties for PV applications. • The present results provide new guidelines and a versatile approach to the design of LC TANIs as a new class of electron donors for solution-processable PV applications. Figure 1. Structure of TANI EB diblock materials. Figure 2. PL spectra (excitation at 555 nm) of 1:1 mol ratio blends (10-5 M solutions) of a) Ph/Ph TANI EB (or) TANI diblock EB derivatives with PC60BM and b) Ph/Ph TANI EB (or) TANI diblock EB derivatives with IC60BM. The expected final results and their potential impact and use of these materials are envisaged in the area of novel active materials for PV devices. The advantages of solution processability combined with lightweight and flexibility of the prepared LC TANI EB materials could lead to better PV performance, as well as lowering installation and maintenance costs. Therefore, the expected outcome of this project will impact on the research community to aid in the development of a low-cost efficient new electron donor material for organic PVs, and, at the same time, benefit the wider society through contributions to efforts to generate the electricity from renewable energy sources. [1] F. J. M. Hoeben et al, Chemical Reviews, 105, 1491-1546 (2005). [2] B. Kippelen et al, Organic Photovoltaics: Mechanisms, Materials, and Devices, S. S. Sun and N. S. Sariciftci (eds), 271-297 (2005).

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