• Gao, Mei
• Qin, Tianshi
• Pisula, Wojciech
• Mullen, Klaus
• Chen, Ming
• Watkins, Scott
• Wilson, Gerry
• Baumgarten, Martin
• Zajaczkowski, Wojciech

Abstract

Extensive efforts have been made to develop novel conjugated polymers that give improved performance in organic photovoltaic devices. The use of polymers based on alternating electron donating and electron accepting units allows the frontier molecular orbitals to be tuned to maximise the open-circuit voltage of the devices. By contrast, far less effort has been devoted to controlling the other critical device parameter – the short circuit current. In fact, varying the non-chromophoric components of a polymer is often secondary to the efforts to tune the molecular orbitals. Here, we introduce an approach to polymer synthesis that facilitates simultaneous control over the structural and electronic properties of the polymers. Through the use of tailored donor-acceptor macromonomers, that enable variations in the donor fragment substituents, we can control both the polymer tacticity and solubility. This control results in improved intermolecular π-stacking interactions and therefore enhanced charge-carrier mobility. Solar cells using the solubilised, syndiotactic polymer show short-circuit current densities that are twice that of the simple, atactic analogue while still maintaining an identical open-circuit voltage. Tailored donor-acceptor macromonomers therefore represent a promising new approach to the synthesis of materials for high efficiency organic photovoltaic devices.

Topics

• impedance spectroscopy
• polymer
• mobility
• laser emission spectroscopy
• tacticity