ABSTRACT
The relationship between the structure of the charge-separation interface and the photovoltaic performance of all-solid dye-sensitized solar cells is reported. This cell is composed of porous a TiO2/perovskite (CH3NH3PbI(x)Cl(3-x))/p-type organic conductor. The porous titania layer was passivated with Al2O3 or Y2O3 to remove surface traps of the porous titania layer. Both passivations were effective in increasing the efficiency of the solar cell. Especially, the effect of Y2O3 passivation was remarkable. After passivation, the efficiency increased from 6.59 to 7.5%. The increase in the efficiency was discussed in terms of the electron lifetime in TiO2, the thermally stimulated current, the measurement of the microwave refractive carrier lifetime, and transition absorption spectroscopy. It was proven that surface passivation resulted in retardation of charge recombination between the electrons in the porous titania layers and the holes in the p-type organic conductors.
ABSTRACT
The charge separation and charge recombination dynamics in P3HT-ZnO and P3HT-dye-ZnO bulk heterojunction organic-inorganic hybrid solar cells (OIHSCs) prepared by a one-pot method were studied using a transient absorption (TA) method, both for optical absorption of P3HT in the visible region and for optical absorption of SQ36 in the NIR region. In the case of P3HT-ZnO, the charge separation was very fast, occurring within 1 ps. On the other hand, high charge recombination between electrons in the surface states and/or the conduction band of ZnO and holes in P3HT was observed. In the case of P3HT-dye-ZnO, we found that the charge recombination could be greatly suppressed by locating the dye at the P3HT/ZnO interfaces while maintaining a fast charge separation rate (a few ps to 10 ps). Our findings provide one methodology for the design of OIHSCs for improving their conversion efficiency, which is to position the dye at the appropriate BHJ interfaces.
