Effect of Ultrathin Al2O3 Layer on TiO2 Surface in CdS/CdSe Co-Sensitized Quantum Dot Solar Cells

摘要

In order to enhance the photovoltaic property of the CdS/CdSe co-sensitized quantum dot sensitized solar cells (QDSSCs), the surface of nanoporous TiO2 photoanode was modified by ultrathin Al2O3 layer before the deposition of quantum dots (QDs). The Al2O3 layer, dip-coated by 0.10 M Al precursor solution, exhibited the optimized performance in blocking the back-reaction of the photo-injected electrons from TiO2 conduction band (CB) to polysulfide electrolyte. Transient photocurrent spectra revealed that the electron lifetime (τ_e) increased significantly by introducing the ultrathin Al2O3 layer on TiO2 surface, whereas the electron diffusion coefficient (D_e) was not varied. As a result, the V_(oc) increased from 0.487 to 0.545 V, without appreciable change in short circuit current (J_(sc)), thus inducing the enhancement of photovoltaic conversion efficiency (η) from 3.01% to 3.38%.