Designed amphiphilic fullerene morphologies with optical and electronic control for bottom up functional photovoltaics
Though fullerenes have been revolutionizing photovoltaic technology over the last decades,20, 188190 they are being replaced by nonfullerene acceptors.28, 191 Albeit many upsides of fullerenes ranging from multiple charge acceptance to isotropic charge mobility are commendable; downsides like low visible light absorption and poor tunability of electronic energy levels and high cost are limiting their usability. Some earlier research was targeted towards the synthesis of structurally elegant and functional fullerene assemblies bound by multiple noncovalent interactions.48, 192 However, just a few research on van der Waals (vdW) dimers and photopolymerized fullerenes unveiled presence of charge traps149 and high electron affinities67 which are detrimental for photovoltaic performance. This early research has initiated the development of a holistic framework to understand how supramolecular structure determines optoelectronic properties. This has been the prime scientific challenge in fullerene electronics in the recent years.192 This thesis not only ddresses the above mentioned challenge and bridges the gap between single molecule and device level, but strives to reach the grand target of alleviating the fundamental limitations of fullerenes (also see Figure 11 and Figure 12). This is done by tailoring the optoelectronic properties of the amphiphilic fullerene derivative MPEGC60, by supramolecular structural control on thin solid films.