Para-halogenated triphenyltriazine induced surface passivation toward efficient and stable perovskite solar cells

Surface passivation is a practical approach to improve the efficiency and stability of perovskite solar cells (PSCs). In this paper, we introduce para-halogenated triphenyltriazine (TRZ-X, X = F, Br, I) to modify the perovskite absorbers. As the core of TRZ-X, 1,3,5-Triazine has abundant C = N bonds, which can produce intermolecular interactions with uncoordinated Pb2+. The halogen atoms as peripheral unit of TRZ-X with strong electronegativity can not only generate ionic bonds with Pb(2+ )in the perovskite but also form a stable rigid plane with the TRZ group. Under the synergy effect of C = N bonds and halogen atoms, the defect density of perovskite films is effectively decreased, contributing to the power conversion efficiency (PCE) and stability of devices. Moreover, the presence of TRZ-X hydrophobic passivation layer could prevent moisture penetration, which is beneficial to long-term stability of PSCs. Due to the strong electronegativity, TRZ-F modified device presents the best PCE of 19.81% compared with that (18.32%) of control device. In addition, TRZ-F passivated and unencapsulated device retains 81% of the initial PCE after 1200 h storage under ambient condition with a relative humidity of 70%, whereas the pristine device decays to 59% of the initial PCE under the same conditions.

Automated summary

Surface passivation is an effective method to improve the efficiency and stability of perovskite solar cells. In this study, the researchers introduced a compound called TRZ-X to modify the perovskite absorbers. The unique structure and properties of TRZ-X effectively reduced the defect density of the perovskite film and prevented moisture penetration, resulting in improved power conversion efficiency and long-term stability of the devices.