Triphenyl Imidazole-Phenothiazine Dual-Donor Organic Dyes With I-/I3 - Redox Couples for Highly Efficient Indoor Dye-Sensitized Photovoltaics.

Abstract

Dye-sensitized solar cells are gaining recognition as a promising technology increasingly drawing the interest of a burgeoning array of IoT devices and wireless sensors, providing a solution to the escalating need for cordless power. We have chosen four organic sensitizers incorporating triphenyl imidazole and phenothiazine as double donors alongside a carboxylic acid as an anchoring group. Sensitizers have either benzothiadiazole (LG-P6 and LG-P8) or phenyl (LG-P5 and LG-P6) as an auxiliary acceptor, separated from the anchoring carboxylic acid group by an ethynyl bridge. The devices are fabricated using the I^-/I₃ ^- redox couple and evaluated under AM1.5G and indoor light conditions. The sensitizers having benzothiadiazole displayed efficiency of 5.98% and 2.81% under 1-sun conditions. Further, we have systematically evaluated device performance from 1000 to 100 lx WW CFL, WW LED, DL CFL, and DL LED light conditions. We observed efficiencies of 19.73% under 1000 lx WW CFL and 24.23% under 100 lx WW LED conditions using the LG-P6 sensitizer, which is one among the highest efficiencies reported without cosensitization to the best of our knowledge. Further, we adopted interfacial charge transfer studies using different perturbation techniques to explain the photovoltaic results.