Tandem DSSC fabrication by controlled infiltration of organic dyes in mesoporous electrode using electric-field assisted spray technique

Abstract

Tandem absorber architectures in DSSCs for extending the light absorption range, using two dyes (N719/Red dye and N749/Black dye) appropriately infiltered in the pores of a mesoporous TiO2 photoanode, have been prepared for the first time by electric-field assisted spray technique (E-Spray). In comparison to the conventionally used dip technique, which takes several hours the E-spray technique developed in this study significantly reduces the loading time to 10–15 min by rapid pore filling of dual dyes. The shorter wavelength (450–550 nm) absorber -N719 dye and longer wavelength (550–800 nm) absorber -N749 dye have been infiltrated sequentially and in right proportion by precise control over E-Spray parameters in order to capture a wider range of the incident solar spectrum. The tandem DSSCs (T-DSSCs) thus fabricated show substantial improvement in photo-current density (Jsc), resulting in ~11% enhancement in photoconversion efficiency (PCE), as compared to a single-dye device. The best performing T-DSSC (N719:N749-75:25) yields the Jsc, Voc and FF of ~16 mA/cm2, ~0.75 V and ~0.69, respectively, resulting in PCE of 7.5%, which is ~40% higher than the PCE of 5.33% for the conventionally fabricated dip-coated DSSC. This study opens up door for tandem device fabrication using E-spray technique which is suitable for large area and roll-to-roll manufracturing aiming for high PCE solar cells.