Synthesis of Cobalt-Doped TiO2 Based on Metal–Organic Frameworks as an Effective Electron Transport Material in Perovskite Solar Cells

摘要

In this study, Co-doped TiO2 was prepared successfully using a solvothermal method with trimesic acid (H3BTC) as an organic framework to form the Co-doped Ti metal–organic framework (Co-doped Ti-MOF). By thermally decomposing the Co-doped Ti-MOF in air, the framework template was removed, and porous Co-doped TiO2 was obtained. The crystal structure of the material was analyzed using X-ray diffraction. The morphology was examined using scanning electron microscopy (SEM) and focused ion beam SEM. The large specific surface area was determined to be 135.95 m2 g–1 using Brunauer–Emmett–Teller theory. Fourier transform infrared spectroscopy verified the presence of Ti–O–Ti and Co–O vibrations in the as-prepared sample. Furthermore, the results of UV–vis spectroscopy showed that doping with Co remarkably improved the absorption ability of Ti-MOF toward the visible-light region with a band gap energy of 2.38 eV (λ = 502 nm). Steady-state photoluminescence and electrochemical impedance spectroscopy were conducted to illustrate the improvement of electron transfer in the doped material further. The optimum power conversion efficiency of solar cells using 1 wt % Co-doped TiO2 as an electron transport layer was found to be 15.75%, while that of solar cells using commercial dyesol TiO2 is only 14.42%.