Kim H.,Hanyang UniversityGyeonggi do |
Choi Y.,Materials & Components Technology Center |
Park Y.,Hanyang UniversityGyeonggi do |
Pawar R.C.,Hanyang UniversityGyeonggi do |
And 2 more authors.
Current Applied Physics | Year: 2017
Porous TiO2 films were deposited onto FTO (fluorine doped tin oxide) substrate through dry deposition method, and polystyrene (PS) beads used as a sacrificial material. In addition, pore size was controlled by introducing 50-nm- and 300-nm-sized PS beads. Moreover, the improved porous film was obtained by varying weight ratios of TiO2 and PS powders to enhance DSSCs (dye-sensitized solar cell) efficiency. The DSSC with improved porous structure has shown efficiency of 6.8% with weight ratio (71.5%), which higher than that of only TiO2 layer (6.08%) and other compositions. The IPCE analysis showed the maximum absorbance over the wavelength range of 550–800 nm resulted in higher efficiency. EIS results indicated that the electron generation and transfer properties of porous films were better than that of the TiO2 layer only. From photovoltage decay measurement, the carrier lifetime was found to be longer in the porous structure than that of TiO2 layer only. Then, we proposed formation mechanism of porous films and their relation for effective scattering/absorbance of light. Moreover, the porous structure also enhances the specific surface area for higher amount of dye loading. Therefore, deposition of porous films could improve the efficiency of DSSCs using facile process. © 2017 Elsevier B.V.
Acter S.,Hanyang UniversityGyeonggi do |
Cho J.,Hanyang UniversityGyeonggi do |
Kim J.W.,Hanyang UniversityGyeonggi do |
Byun A.,Hanyang UniversityGyeonggi do |
Park K.-H.,Hanyang UniversityGyeonggi do
Bulletin of the Korean Chemical Society | Year: 2015
This paper introduces a straightforward and robust polymerization method for the synthesis of uniform polymer microparticles having controlled surface chemistry as well as tailored particle shapes. Uniform polystyrene (PS) microparticles are produced by dispersion polymerization, in which amphiphilic poly(ethylene oxide)-b-poly(ε-caprolactone) (PEO-b-PCL) copolymers anchor on to the growing polymer particles and stabilize them by steric repulsion. We have observed that, when PEO-b-PCL copolymers are incorporated at the proper concentration range, the total number of particles remains unchanged after the formation of primary particles, which is essential for maintaining size uniformity. Otherwise, nonuniform PS microparticles are produced mainly as a result of the coagulation or secondary formation of particles. To show the diversity of our particle synthesis technology, shape-controlled microparticles, such as dimples and Janus particles, are also produced by using temperature-mediated swelling and phase separation. Finally, we show that PEO-b-PCL copolymers play a key role in regulating the surface wettability of the seed particles, thereby facilitating the formation of anisotropic microparticles. © 2015 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.