Expanding the absorption and photoresponse of 1D lead–halide perovskites via ultrafast charge transfer

Low-dimensional metal halide perovskites are attracting extensive attention due to their enhanced quantum confinement and stability compared to three-dimensional perovskites. However, low dimensional connectivity in the inorganic frameworks leads to strongly bounded excitons with limited absorption properties, which impedes their application in photovoltaic devices. Here, we show that, by incorporating a strong electron accepting methylviologen cation, charge transfer (CT) at the organic/inorganic interface can effectively tune the optical properties in one-dimensional (1D) lead-halide perovskites. Both 1D MVPb2I6 and MVPb2Br6 display expanded absorption and photoresponse activity compared to CT inactive cations. The photoinduced CT process in MVPb2I6 was further characterized by transient absorption spectroscopy, which shows an ultrafast CT process within 1 ps, generating charge separated states. Our work unveils the interesting photophysics of these unconventional 1D perovskites with functional organic chromophores.