Microscopy of Hierarchically Organized TiO2 Photoelectrode for Dye Solar Cells

Research on improving the performance of dye solar cells has various aspects of the device being investigated. This paper analyzes the deliberately hierarchized photoelectrode configuration for DSC applications to improve the performance of DSCs. Multiple layers of differently composed TiO2 particle types namely aggregates and nanoparticles were deposited to form a photoelectrode with thickness of about 12 mu m. The photoelectrodes were assembled into working DSCs with an active area of 1 cm(2). Measurement for solar power conversion performance was measured under 1 sun at AM1.5 spectrum simulated sunlight. Electron microscopy for photoelectrode analysis was conducted using Field Emission Scattering Electron Microscopy with enhanced resolution. External Quantum Efficiency was measured using a purpose built instrument. Kinetics were investigated using the Electrochemical Impedance Spectroscopy (EIS) measurement with a potentiostat. The best performing DSC is of the hierarchically organized photoelectrode with a photoconversion efficiency of 4.58%, an increase of 14% in comparison to the reference samples with fully aggregates configuration. Short circuit current density, J(sc) increases by about 2.223 mA cm(-2) relative to the blanks. The electron microscopy confirmed expected thickness at around 10 mu m and layers forming the photoelectrode being hierarchically deposited with similar to 20 nm TiO2 nanoparticles and 450 nm TiO2 aggregates mixture composition. EQE improved especially for visible region of 500550 nm light wavelengths with 12 % increase in the response of in that region. Improvement to the diffusion coefficient as measured by the EIS contributed to the performance increase of the photoelectrode configuration under investigation.