Green vegetables derived simultaneously carbon dots as sensitizer and carbon particles as counter electrode for dye-sensitized solar cells

Carbon materials for dye-sensitized solar cells (DSSC) have aroused much attention recently due to their low cost, wonderful chemical stability and outstanding catalytic activity, etc. As China is a large agricultural country, in consideration of environmental protection and low cost, two common green vegetables, including cucumber and green pepper, are employed to prepare carbon quantum dots (CQD) by hydrothermal method, and simultaneously the residues are carbonized to obtain carbon particles (CP) in this study. The optical performances of the as-prepared CQD were acquired through UV-Vis and PL tests, showing that the CQD were suitable as sensitizers for DSSC. Thereby CQD-based DSSC with Pt counter electrode (CE) were experimentally fabricated, yielding the power conversion efficiency (PCE) of 0.21% and 0.28% respectively under AM 1.5 one sun illumination. Meanwhile, the CP were coated on FTO as CE for DSSC, and the favorable electrochemical properties of the CP-based CE were measured by EIS and Tafel. Therefore the CP-based DSSC with N719 sensitizer were constructed, and achieved the PCE of 1.45% and 1.40% respectively. The above results distinctly present the photovoltaic applications of CQD and CP concurrently derived from green vegetables as sensitizer and counter electrode for DSSC, which indicate the prospect for the realization of high-performance photovoltaic cells from low cost and environmentally friendly natural products.