Block copolymer design for morphology control in organic photovoltaics
Valerie Mitchell a, David Jones a
a University of Melbourne, School of Chemistry & Bio21 Institute, 30 Flemington Road, Parkville, Victoria, 3010
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
Kyōto-shi, Japan, 2019 January 27th - 29th
Organizers: Hideo Ohkita, Atsushi Wakamiya and Mohammad Nazeeruddin
Oral, Valerie Mitchell, presentation 030
DOI: https://doi.org/10.29363/nanoge.iperop.2019.030
Publication date: 23rd October 2018

While inorganic solar cells enjoy a level of success, high manufacturing costs and bulky modules limit their broad applicability. In contrast, organic photovoltaic (OPV) devices employ flexible thin-films of organic small molecules or polymers as the photoactive layer. OPV could provide a low-cost alternative to traditional PV, and a system of solution processing coupled with roll-to-roll printing of lightweight, flexible solar cells is envisioned. However, current OPV technology relies on precise control of the domains and orientations of the organic molecules in the active layer, and these are difficult to achieve and maintain with processing techniques during printing. Furthermore, many high-performance OPV materials rely on toxic solvents for processing which is not environmentally appealing.

In this research we address these shortcomings through the use of amphiphilic block copolymers as active layer materials. Block copolymers are well-known for their ability to adopt regular morphological structures in thin-film, controllable by varying the structure of the polymer components.1 Careful design can ensure that desired morphologies are thermodynamically favoured, leading the polymers to readily adopt and maintain the ideal conformations. Amphiphilic block copolymers, in which hydrophilic moieties are incorporated into one block, are thermodynamically more likely to undergo phase separation into well-defined morphologies. Additionally, the suitably chosen hydrophilic moieties can increase the solubility of the active layer material in green solvents. In this work, we demonstrate the benefit of the amphiphilic block copolymer systems and their spontaneous adoption of thermally stable morphologies when deposited from industrially relevant solvents.2,3 We then use X-ray scattering techinques to examine the interplay between phase separation, crystallinity, and device performance in two novel block copolymer materials.

 

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