Luminescence and molecular modelling as tools to probe structure-property-performance relationships at molecular heterojunctions
Jenny Nelson a
a Imperial College London, Physics Department and Center for Processable Electronics
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Keynote, Jenny Nelson, presentation 191
Publication date: 20th April 2022

In a molecular photovoltaic device, charge separation and energy conversion result from the evolution of a photogenerated exciton into a charge separated state, in competition with recombination to ground. Recently, new molecular materials have led to steady increases in power conversion efficiency that now appoach 20%. To make further advances, we need to understand and isolate the effects of chemical structure, molecular packing, energetics and disorder on the competition between charge separation and recombination and hence on device efficiency. Electro- and photo-luminescence have proved to be valuable tools to probe the energy and dynamics of excited states involved in photoinduced charge separation, and to study structural and energetic disorder at molecular interfaces. The combination luminescence with other spectroscopic techniques, transient electrical measurements and computational modelling can be effective in helping us to understand how chemical and physical structure control the basic mechanisms of a photovoltaic device. Such an approach can be used to study the properties and role of charge transfer states, and the impact of structural and energetic disorder. We show how an integrated computational model allows different experimental measurements to be reconciled within a single picture and helps to show how the properties of interfacial states control the device [1]. We use our results to consider the ultimate limitations placed on solar to electric conversion by the molecular nature of the materials.

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