Yiduo Zhang

Study on the effect of measuring methods on incident photon-to-electron conversion efficiency of dye-sensitized solar cells by home-made setup

An experimental setup is built for the measurement of monochromatic incident photon-to-electron conversion efficiency (IPCE) of solar cells. With this setup, three kinds of IPCE measuring methods as well as the convenient switching between them are achieved. The setup can also measure the response time and waveform of the short-circuit current of solar cell. Using this setup, IPCE results of dye-sensitized solar cells (DSCs) are determined and compared under different illumination conditions with each method. It is found that the IPCE values measured by AC method involving the lock-in technique are sincerely influenced by modulation frequency and bias illumination. Measurements of the response time and waveform of short-circuit current have revealed that this effect can be explained by the slow response of DSCs. To get accurate IPCE values by this method, the measurement should be carried out with a low modulation frequency and under bias illumination. The IPCE values measured by DC method under the bias light illumination will be disturbed since the short-circuit current increased with time continuously due to the temperature rise of DSC. Therefore, temperature control of DSC is considered necessary for IPCE measurement especially in DC method with bias light illumination. Additionally, high bias light intensity (>2 sun) is found to decrease the IPCE values due to the ion transport limitation of the electrolyte.

Quasi-solid-state dye-sensitized solar cell fabricated with poly (β-hydroxyethyl methacrylate) based organogel electrolyte

A novel freestanding poly (β-hydroxyethyl methacrylate), PHEMA-based organogel electrolyte is developed simply by optimization of the solution polymerization in the same solvent as the organic electrolyte for dye-sensitized solar cells (DSCs). The room temperature ionic conductivity of the gel electrolyte is 4.54 × 10−3 S cm−1, and the conduction behavior can be well described by the free volume model. The quasi-solid-state dye-sensitized solar cell fabricated with this PHEMA-based polymer gel electrolyte can present high energy conversion efficiency up to 7.5%. Preliminary long-term stability test further reveals that this quasi-solid-state electrolyte exhibits good stability after 1000 h thermal test in comparison with the DSCs based on corresponding liquid electrolyte.

In situ optical microspectroscopy monitoring of binary colloidal crystal growth dynamics via evaporation-induced cooperative self-assembly.

Real-time monitoring of the binary colloidal crystal (bCC) growth via evaporation-induced cooperative self-assembly (EICSA) was studied by an in situ optical microspectroscopy technique. Evolution of the recorded reflectance spectra reveals that the whole growth process of bCCs via EICSA could be separated into three different stages corresponding to that of unary colloidal crystals because of the same evaporation model. We show the detailed cooperative self-assembly information, including the evolution of the number of layers and filling factors of different components of the growing bCCs using the scalar wave approximation method. Furthermore, when the size ratio and number ratio of the two colloids were varied, the real-time optical properties of the bCCs with various stoichiometric configurations were investigated systematically. This study would be valuable in furthering the current understanding of the bCC growth dynamics via EICSA and tailoring optical properties of hierarchical materials for applications in many fields.