Since Grätzel first reported ruthenium-based sensitizers in 1991, dye-sensitized solar cells (DSSCs) have been in the center of widespread interest. The past decade has witnessed a rapid development in porphyrin dyes with high molar extinction coefficients and strong absorption in a broad wavelength range, envisaging wide-range applications. However, the major obstacle is porphyrin's typical absorption defects in the regions of λ=350–410 and 500–600 nm. To address this challenge, co-sensitization method becomes an attractive choice to build high performance panchromatic DSSCs. Herein, we unraveled a novel donor-π-acceptor (D-π-A) system of 7H-Dibenzo[c,g]carbazole and fused Zn-porphyrin FW-1 with "push-pull" molecular structure, and co-sensitized it with indoline dye WS-5 which has high light-harvesting capability in the regions of λ=350–420 and 450–650 nm. Results indicate that compared to single sensitizer, FW-1+WS-5 shows a remarkable breakthrough in PCE from 6.53 and 7.05% to 10.22 and 10.42% based on I-/I3- and [Co(bpy)3]2+/3+electrolytes, respectively, and 10.80% under 0.79 sun irradiation with cobalt electrolyte. To shed light on adsorption model speculated in co-sensitization process, extensive first-principles density functional theory (DFT) calculations were performed. The absorption valley of FW-1 was compensated and computationally illustrated to show the first electronic transition at λ=477 nm (78% from HOMO→LUMO transition of WS-5). With these data in hand, we sought to investigate photovoltaic performance of FW-1+WS-5-based DSSCs under AM 1.5G irradiation (100 mW/cm2). For cobalt electrolyte, short-circuit current density (JSC)=18.25 mA/cm2, open-circuit voltage (VOC)=840 mV, fill factor (FF)=0.68; for iodine electrolyte, JSC=18.90 mA/cm2, VOC=761 mV, FF=0.71. Being easy-to-construct, with superior efficiency, FW-1+WS-5 co-sensitization system offers a new avenue in the amelioration of DSSCs.

High-performance porphyrin-based dye-sensitized solar cells with iodine and cobalt redox shuttles

255th National Meeting (2018)

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