A Heteronuclear W/Cu/S Clusters-Based Donor-Acceptor Polymer for Perovskite Solar Cells

Donor-acceptor polymers containing the repeating moiety of electron-rich unit (donor) and electron-deficient group (acceptor), impair their highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) considerably localized on the donors and acceptors, respectively. Their band gaps can be well-tuned by the electron-donating ability of donors and the electron-withdrawing ability of acceptors. The efficient splitting of photo-generated excitons by electronic pull-push effect between donor and acceptor could promote the effective charge transport within polymer. Therefore, donor-acceptor polymers have the merits of versatile molecule structure, accessible functionalization, and adjustable electronic structure, becoming one of the most promising organic optoelectronic materials. For instance, by adjusting the alternating array of donor and acceptor moieties, a series of donor-acceptor polymers with lower band gaps and good light-harvesting ability are prepared and used as potential photoelectronic materials. Designing the donor-acceptor polymers-based modifiers with good charge mobility and abundant surface functional groups to bind on perovskite material is highly demanded to boost interfacial charge extraction and transport while yet realized. Here, two [WS4Cu4Br]+ and [WS4Cu5Br2]+ cluster units are bridged by triphenylamine ligands to yield an unprecedented a heteronuclear W/Cu/S clusters-based donor-acceptor polymer. Due to the effect of Rydberg orbital components in different clusters mainly contributed by Cu ions, Cu-rich units have negative potential, whereas Cu-deficient groups display positive potential. This facilitates the formation of a circuit network with ligands acting as "wires" to realize efficient charge transport. Mobility tests reveal that the hole mobility of polymer film is 3.81 x 10-5 cm2 V-1 s-1. Such a polymer can efficiently extract and transport the holes from perovskite film, and thus improving the cell performance and stability. This work opens the opportunities for designing donor-acceptor polymers based on heteronuclear W/Cu/S clusters. image