고체 고분자 전해질을 이용한 염료감응 태양전지에서 산화주석 나노입자의 물리 화학적 효과 영향

Abstract

The metal oxide nanofillers (SnO2, <100 nm) are added into the polymer electrolyte to enhance both the photocurrent and photovoltage in Dye-sensitized solar cells (DSCs). It has been well known that the nanofillers play many different roles. In the case of oligomeric electrolyte of polyethylene golycol (PEG), the metal oxide nanofillers induce the increase in the ionic conductivity by free volume generation at the interface and concomitantly the increase in viscosity. Since the SnO2 nanoparticles (NPs) show Lewis acidic properties, they would have additional functions. For example, they may be surrounded by cations such as K+, Li+ or Li+ first because of the acidic properties of the SnO2 surface and subsequently by anions such as I3- and I- to provide electro-neutrality. Note that the size of the nanofillers (100 nm) is much bigger than the common size of nanopores (< 20 nm) in the common TiO2 layer and therefore the nanofillers are present only in the bulk rather than the nanopores. Therefore, the I3- species may stay preferentially at the surface of the nanofillers because of the acidic properties of the SnO2 nanofillers. In other words, the I3- concentration may be less in the nanopores than in the bulk, which may strongly affect the photovoltaic performance of DSCs such as TiO2 conduction band (CB)-edge shift, electron recombination, light absorption of dye, etc. As a result, the SnO2 nanofillers increase both the photocurrent and the photovoltage, resulting in the increase in the overall energy conversion efficiency of the cells.