Metal-Free Organic Dyes with Double Auxiliary Acceptors for High-Performance Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have continuously received attentions in the field of photovoltaics due to their charming properties and promising performance under the indoor dim-light environment. Herein, two organic photosensitizers (<bold>GZ121</bold> and <bold>GZ124)</bold> are designed with the insertion of double auxiliary acceptors in a donor-acceptor-pi-acceptor-pi-acceptor (D-A-pi-A-pi-A) design. The devices fabricated from these photosensitizers are investigated under one sun and dim-light (300-6000 lux) conditions with <bold>N719</bold> dye for comparison. The <bold>GZ124</bold> dye achieves power conversion efficiencies (PCEs) of 9.43% (photocurrent density (J(sc)) = 14.79 mA cm(-2), photovoltage (V-oc) = 0.85 V, and fill factor (FF) = 0.75) under one sun irradiation and 28.62% (J(sc) = 0.99 mA cm(-2), V-oc = 0.68 V, and FF = 0.77) under dim-light illumination at 6000 lux, which is far better than the reference <bold>N719</bold> dye. Moreover, the PCE under dim light is ranked among the top as compared to DSSCs devices sensitized by a single dye. The <bold>GZ124</bold> dye also demonstrates outstanding stability for more than 1000 h under prolonged one sun sensitization. The current studies affirm that the design of a D-A-pi-A-pi-A structural framework by introducing double auxiliary acceptors in a single sensitizer is a promising approach to boost the performance of DSSCs.