Elucidating the Role of the Metal Linking Ion on the Excited State Dynamics of Self-Assembled Bilayers

作者：Wang Jamie C; Ogunsolu Omotola O; Sykora Milan; Hanson Kenneth^*

来源：Journal of Physical Chemistry C, 2018, 122(18): 9835-9842.

DOI：10.1021/acs.jpcc.8b02387

Metal ion-linked, self-assembled multilayers on nanocrystalline metal oxide surfaces have recently emerged as an effective strategy for manipulating energy and electron transfer dynamics at organic-inorganic interfaces. The choice of metal ion can have a large impact on the stability, loading concentration, and other properties of the films. Here we report our investigation into the role of the linking ion on the subnanosecond excited state dynamics in the bilayer films (TiO2-B-M-RuP). While metal linkers like Cd-II, La-III, Sn-IV, Zn-II, and Zr-IV are photochemically inert, paramagnetic linking ions such as C-II, Fe-II, and Mn-II quench the excited state of the dye with a rate constant on the order of 10(8) s(-1). The absence of new spectral features in the transient absorption spectrum suggests that energy transfer, and not electron transfer, is responsible for the excited state quenching. On TiO2, the electron injection rate for TiO2-B-M-RuP is an order of magnitude slower (similar to 1 X 10(9) s(-1)) than for the dye directly on TiO2 (similar to 3 X 10(10) s(-1)) due to increased spatial separation and reduced electronic coupling between the dye and the surface. In dye-sensitized solar cells, the TiO2-B-M-RuP devices exhibit a notably lower J(sc) but higher V-oc compared to TiO2-RuP with even lower photocurrents for Cu-II, Fe-II, and Mn-II bilayers presumably at least in part due to competitive quenching of the excited state by the metal ion. The increases in V-oc are offset by the decrease in J(sc); thus, the overall efficiency of the bilayer devices is lower than the that of the parent, monolayer device.

• 出版日期2018-5-10
• 单位Los Alamos