Simple organic dyes containing multiple anchors as effective co‐sensitizers for DSSCs loaded with Ru (II) complex N‐719

Abstract

In this work, we report a comprehensive photovoltaic investigation of eight pure organics, structurally simple, and low‐cost 2‐cyano‐N‐thiazolyacrylamide dyes (AM‐1‐8) co‐sensitizers for dye‐sensitized solar cells (DSSCs) with the standard Ru (II) dye (N‐719). A co‐sensitization strategy has been applied for enhancing the performance of DSSCs wherein a Ru (II) metal complex is combined with a simple type of the designed organic metal‐free dyes (AM‐1‐8). The co‐sensitization by the absorption of co‐sensitizers AM‐1‐8 leads to a broader light‐harvesting ability (300–750 nm) and scored photovoltaic efficiency at a range of 6.08%–9.30%. Upon co‐sensitization, the device made of bis(2‐cyanoacetamide) co‐sensitizer AM‐7 system yielded the highest power conversion efficiency (PCE) = 9.30% with JSC = 20.96 mA/cm2, VOC = 0.73 eV, and FF = 60.78 that outperformed the standard dye (N‐719). N‐719 dye only showed PCE of 7.30% with JSC = 18.68 mA/cm2, VOC = 0.64 eV, and FF = 61%. The great enhancement of the effect of the co‐sensitizer AM‐7 on the N‐719 can be related to the enhancement of both short current density (JSC) and open circuit voltage (VOC). The greater JSC value can be attributed to the maximum dye loading value of this dye on the TiO2 surface (3.76 × 10−5/mol cm−2) as a result of the presence of bis‐anchoring function within the dye molecule. The increase in the VOC value can be attributed to its highest recombination resistance because of the multi‐anchoring groups, which was confirmed by electrochemical impedance spectroscopy (EIS). Theoretical density functional theory (DFT) and highest occupied molecular orbital (HOMO)‐ lowest unoccupied molecular orbital (LUMO) energy were performed to study the electron density distribution between donor and acceptor moieties. All the multi‐anchoring functions presented in bis(2‐cyanoacetamide) and 2‐cyanacrylamide co‐sensitizers demonstrate promising co‐sensitizers for excellent photovoltaic performance response on the standard dye (N‐719).