Metal‐organic framework coordinated with cobalt ion as charge recombination retarder in dye‐sensitized solar cells

Summary The photoanode of the conventional dye‐sensitized solar cell (DSSC) is modified, by depositing a layer of cobalt‐metallic‐ion‐coordinated metal–organic framework (Co‐MOF199) on top of the regular titanium‐dioxide film. The results of electrochemical impedance spectrum (EIS) indicated that the presence of Co‐MOF199 layer in the photoanode of DSSC brought about an increase in the electron recombination lifetime (time to the electrons to recombine with the cations) and, consequently, the increase in electron recombination resistance (Rrec) in the photoanode electrolyte interface. The increased recombination resistance is attributed to the efficient retardation of the rapid recombination between photo‐induced electrons and transient cations in DSSC. These positive changes in the photoanode electrolyte interface of DSSC resulted in the increase in open‐circuit voltage (Voc), which accounts for the ultimate 20% enhancement in the power conversion efficiencyη, compared to the conventional DSSC. A total of six Co‐MOF199 concentration variants of DSSC configurations coated by soaking and spin coating were fabricated, and it was observed that [TiO2 + N3/Co‐MOF199 (30 mM)/Pt] DSSC configuration (soaked), in particular, exhibits the best photovoltaic parameters with Voc ~ 827 mV, Rrec ~ 170 Ω, and η ~ 8.38%, compared to the conventional DSSC, where Voc ~ 758 mV, Rrec ~ 76 Ω, and η ~ 6.91%. In addition to photovoltaic characterizations, morphological, elemental, and crystallographic characterizations of the Co‐MOF199‐coated photoanodes were carried out. Schematic diagram of Co‐MOF199‐based DSSC