Tetraphenylethylene tethered phenothiazine-based double-anchored sensitizers for high performance dye-sensitized solar cells

Abstract

Double-anchored phenothiazine-cored sensitizers (YL1–YL4) having a tetraphenylethylene (TPE) entity as the N-substituent with various π-spacers (thiophene, 3-hexylthiophene, 4-hexyl-2,2′-bithiophene, and 4-heptyl-4-hexyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophene) are prepared for dye-sensitized solar cells (DSSCs). The YL4-based DSSC exhibits the best solar-to-electricity conversion efficiency of up to 9.79% and 10.87%, respectively, without and with the CDCA co-adsorbent. These values outperform the efficiencies of cells based on N719 (8.77%) and our previous outstanding double-anchored phenothiazine-cored dye (HL5, 8.53%). YL dyes possess double layered shelters for efficient blockade of dark current: the inner shelter from the dianchor skeleton and the outer shelter from clogged TPE units. Clogged TPEs also strengthen dye stability on the TiO₂ surface. Under room light illumination (Philips T5 lamp), the YL4-based DSSC device exhibited high cell efficiencies of 27.54%, 26.81%, and 24.98% at 187 lux, 597 lux, and 1025 lux, respectively, showing great potential towards the Internet of Things (IoTs).