Linking bridge improvement of ZnO/N719 interfaces via ammonia treatment for efficiency enhancement of dye-sensitized solar cell

Abstract

Modifying the photoelectrodes is an interesting strategy for improving the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). In this study, ZnO films were surface-treated using an NH3 chemical vapor process. After appropriate treatment of the ZnO films, the PCE of the DSSCs was maximized at 2.77%, and the short-circuit current density (Jsc) and open-circuit voltage (Voc) were increased accordingly. These parameters were directly proportional to the dye-adsorption performance, which was enhanced by linking-bridge formation of a ZnO−N=dye complex. The complexes improved the ZnO/N719 dye interfaces and completed the dye adsorption; consequently, the Jsc of the DSSC improved from 7.55 to 8.28 mA/cm2 and the Voc improved from 0.57 to 0.61 V. The linking bridge also facilitated electron transport and reduced the recombination. These effects synergistically enhanced the PCE of the DSSC. Moreover, the NH3 vapor treatment did not significantly affect the morphology, shape, or crystalline structure of the ZnO film. Such a non-destructive post-treatment using the chemical vapor process can potentially realize low-cost, high-performance films for DSSCs and other advanced technologies.