ABSTRACT Volatile electrolytes are a stability concern in dye solar cells (DSCs) due to their ten... more ABSTRACT Volatile electrolytes are a stability concern in dye solar cells (DSCs) due to their tendency for leakage. A composite electrolyte consisting of iodide-based ionic liquid and polyaniline-coated carbon black has been previously reported to provide good current transport while being leakage proof due to a quasi-solid structure and the absence of volatile constituents. In this paper we investigate the operating principle of this type of electrolyte and especially its exceptional feature of operating efficiently without added iodine. The absence of additive iodine is significant due to the fact that it is usually required to form the current carrying the I–/I3– redox couple. We modified an electrolyte mass transport model from the literature to estimate the upper limit for the charge transport capability of the composite electrolyte. Comparison of experimental results with the estimated upper limit for the diffusion limiting current density shows clearly that the high current densities observed experimentally with the composite electrolyte can not be explained with normal diffusion even in the case that every feasible source and transport mechanism of free I3– known until now is considered, including photogeneration of I3–, shortened diffusion layer thickness, impurity I3–, and accumulation of I3– to the photoelectrode from the counterelectrode pores and electrolyte edge regions. This intriguing result suggests a currently unknown I3– source or transport mechanism in this type of DSC.
The journal of physical chemistry letters, Jan 5, 2015
Conductivity of methylammonium lead triiodide (MAPbI3) perovskite was measured on different mesop... more Conductivity of methylammonium lead triiodide (MAPbI3) perovskite was measured on different mesoporous metal oxide scaffolds: TiO2, Al2O3, and ZrO2, as a function of incident light irradiation and temperature. It was found that MAPbI3 exhibits intrinsic charge separation, and its conductivity stems from a majority of free charge carriers. The crystal morphology of the MAPbI3 was found to significantly affect the photoconductivity, whereas in the dark the conductivity is governed by the perovskite in the pores of the mesoporous scaffold. The temperature-dependent conductivity measurements also indicate the presence of states within the band gap of the perovskite. Despite a relatively large amount of crystal defects in the measured material, the main recombination mechanism of the photogenerated charges is bimolecular (band-to-band), which suggests that the defect states are rather inactive in the recombination. This may explain the remarkable efficiencies obtained for perovskite sola...
Single-walled carbon nanotube (SWCNT) networks have emerged as very promising alternative to conv... more Single-walled carbon nanotube (SWCNT) networks have emerged as very promising alternative to conventional transparent conducting oxides (TCO) for optically transparent electrodes, exhibiting comparable sheet resistance and optical transmittance but outperforming TCO in terms of mechanical and chemical robustness. Here the advantages of SWCNT films over conventional indium-tin oxide (ITO) on flexible polyethylene terephthalate (PET) as transparent electrodes will be illustrated for applications in two types of electrochemical devices, namely electrochromic windows and dye solar cells (DSC). Apart from their role as transparent conducting layer, the SWCNT film imparts additional functionality in both cases: electrocatalytic properties for the redox couple (as DSC counter electrode) and better resistance to flexure, improved adhesion and higher porosity for the electrochromic layer (in electrochromic films). SWCNTs were synthesized in a laminar flow aerosol reactor by a floating cataly...
ABSTRACT Volatile electrolytes are a stability concern in dye solar cells (DSCs) due to their ten... more ABSTRACT Volatile electrolytes are a stability concern in dye solar cells (DSCs) due to their tendency for leakage. A composite electrolyte consisting of iodide-based ionic liquid and polyaniline-coated carbon black has been previously reported to provide good current transport while being leakage proof due to a quasi-solid structure and the absence of volatile constituents. In this paper we investigate the operating principle of this type of electrolyte and especially its exceptional feature of operating efficiently without added iodine. The absence of additive iodine is significant due to the fact that it is usually required to form the current carrying the I–/I3– redox couple. We modified an electrolyte mass transport model from the literature to estimate the upper limit for the charge transport capability of the composite electrolyte. Comparison of experimental results with the estimated upper limit for the diffusion limiting current density shows clearly that the high current densities observed experimentally with the composite electrolyte can not be explained with normal diffusion even in the case that every feasible source and transport mechanism of free I3– known until now is considered, including photogeneration of I3–, shortened diffusion layer thickness, impurity I3–, and accumulation of I3– to the photoelectrode from the counterelectrode pores and electrolyte edge regions. This intriguing result suggests a currently unknown I3– source or transport mechanism in this type of DSC.
The journal of physical chemistry letters, Jan 5, 2015
Conductivity of methylammonium lead triiodide (MAPbI3) perovskite was measured on different mesop... more Conductivity of methylammonium lead triiodide (MAPbI3) perovskite was measured on different mesoporous metal oxide scaffolds: TiO2, Al2O3, and ZrO2, as a function of incident light irradiation and temperature. It was found that MAPbI3 exhibits intrinsic charge separation, and its conductivity stems from a majority of free charge carriers. The crystal morphology of the MAPbI3 was found to significantly affect the photoconductivity, whereas in the dark the conductivity is governed by the perovskite in the pores of the mesoporous scaffold. The temperature-dependent conductivity measurements also indicate the presence of states within the band gap of the perovskite. Despite a relatively large amount of crystal defects in the measured material, the main recombination mechanism of the photogenerated charges is bimolecular (band-to-band), which suggests that the defect states are rather inactive in the recombination. This may explain the remarkable efficiencies obtained for perovskite sola...
Single-walled carbon nanotube (SWCNT) networks have emerged as very promising alternative to conv... more Single-walled carbon nanotube (SWCNT) networks have emerged as very promising alternative to conventional transparent conducting oxides (TCO) for optically transparent electrodes, exhibiting comparable sheet resistance and optical transmittance but outperforming TCO in terms of mechanical and chemical robustness. Here the advantages of SWCNT films over conventional indium-tin oxide (ITO) on flexible polyethylene terephthalate (PET) as transparent electrodes will be illustrated for applications in two types of electrochemical devices, namely electrochromic windows and dye solar cells (DSC). Apart from their role as transparent conducting layer, the SWCNT film imparts additional functionality in both cases: electrocatalytic properties for the redox couple (as DSC counter electrode) and better resistance to flexure, improved adhesion and higher porosity for the electrochromic layer (in electrochromic films). SWCNTs were synthesized in a laminar flow aerosol reactor by a floating cataly...
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