Electron hopping in conjugated molecular wires with application to solar cells

Electron transfer through molecular wires underpins numerous research fields, ranging from single-molecule electronics to fundamental biological processes and their application in (bio)electrocatalysis. Here we report a series of 1-3-nm-long ferrocene-terminated conjugated molecular wires, anchored to indium tin oxide electrodes, that exhibit an electron transfer mechanism dominated by hopping (with a β value of 0.043 Å^-1). We show that the nature of the electrode, namely the small energy gap between the electron donor and acceptor, explains the unexpected electron transfer mechanism in these short wires. We demonstrate the applicability of these anchored molecular wires as the hole-extraction layer in a tin perovskite solar cell. We show improved performance in devices employing these molecular wires compared with the more conventional hole-extraction layers typically used in tin perovskite solar cells. This work not only opens avenues for mechanistic investigations of interfacial electron transfer using molecular wires but also showcases their potential impact in applications such as photovoltaics.