D-pi-A Dye System Containing Cyano-Benzoic Acid as Anchoring Group for Dye-Sensitized Solar Cells

A D-pi-A dye (KM-1) incorporating cyanobenzoic acid as a new acceptor/anchoring group has been synthesized for dye-sensitized solar cells (DSCs) with a high molar extinction coefficient of 66 700 M-1 cm(-1) at 437 nm. Theoretical calculations show that the hydrogen bond between -CN and surface hydroxyl leads to the most stable configuration on the surface of TiO2. In addition, the adsorption of the dye on TiO2 follows a Brunauer-Emmett-Teller (BET) isotherm. Multilayer adsorption of KM-1 on TiO2 seems to take place particularly at higher dye concentrations. DSC device using KM-1 reached a maximum incident photon-to-current conversion efficiency (IPCE) of 84%, with a solar to electric power conversion efficiency (PCE) of 3.3% at AM1.5 G illumination (100 mW cm(-2)). This new type of anchoring group paves a way to light harvesting with strong binding to the metal oxide surface. design new dyes that combine good visibl

Influence of the Anchoring Modes on the Electronic and Photovoltaic Properties of D−π–A Dyes

Five new donor−π-bridge−acceptor (D−π−A) organic sensitizers with cyano and/or triple bond substituted benzoic acid as acceptor/anchoring groups were synthesized and tested for their performance in dye-sensitized solar cells (DSCs). The systematic incorporation of a cyano group on the benzoic acid anchoring part and an additional acetylene bond at the para-position to −COOH lead to a variation of the photoelectrochemical properties, electronic transitions, and device performances. Characterization of the molecular structure, the electronic/optical properties of the dyes, as well as their photovoltaic performance in DSCs was accomplished by means of electrochemistry, quantum chemical methods, and various spectroscopic techniques such as photoinduced absorption, steady-state spectroscopy, and time-resolved transient absorption studies on femto- and nanosecond time scales. Thereby, significant dependence of DSCs performances on the substituents and anchoring groups was observed. In general, cyano substituents lead to improved DSCs performances. On the other hand, the insertion of an acetylene linker in combination with a cyano group does not enhance the device efficiencies. Devices composed of a para-cyano benzoic acid as anchor revealed maximum IPCE values of 80% with a PCE of 4.50% at AM 1.5 G illumination (100 mW cm−2) due to retarded charge recombination dynamics

Effect of Extended π-Conjugation of the Donor Structure of Organic D–A−π–A Dyes on the Photovoltaic Performance of Dye-Sensitized Solar Cells

Two new D−A−π-spacer−A organic dyes, KM-10 and KM-11, containing a benzothiadiazole unit in a π-spacer and a cyanoacrylic acid as an acceptor have been synthesized and tested as sensitizers in dye-sensitized solar cells. Structural variations of the donor moiety, i.e., π-extension of the diphenylamine electron-donating groups, gave rise to different photovoltaic efficiencies –7.1% for KM-10 and 8% for KM-11– despite having comparable absorption properties. A detailed investigation, including transient photo- current and photovoltage decay measurement, transient absorption spectroscopy, and quantum chemical methods, provided important conclusions about the nature of the substitution on the photovoltaic properties of dyes

Effect of Extended π‑Conjugation of the Donor Structure of Organic D–A−π–A Dyes on the Photovoltaic Performance of Dye-Sensitized Solar Cells

Two new D–A−π-spacer–A organic dyes, <b>KM-10</b> and <b>KM-11</b>, containing a benzothiadiazole unit in a π-spacer and a cyanoacrylic acid as an acceptor have been synthesized and tested as sensitizers in dye-sensitized solar cells. Structural variations of the donor moiety, i.e., π-extension of the diphenylamine electron-donating groups, gave rise to different photovoltaic efficiencies7.1% for KM-10 and 8% for KM-11despite having comparable absorption properties. A detailed investigation, including transient photocurrent and photovoltage decay measurement, transient absorption spectroscopy, and quantum chemical methods, provided important conclusions about the nature of the substitution on the photovoltaic properties of dyes

Influence of the Anchoring Modes on the Electronic and Photovoltaic Properties of D−π–A Dyes

Five new donor−π-bridge–acceptor (D−π–A) organic sensitizers with cyano and/or triple bond substituted benzoic acid as acceptor/anchoring groups were synthesized and tested for their performance in dye-sensitized solar cells (DSCs). The systematic incorporation of a cyano group on the benzoic acid anchoring part and an additional acetylene bond at the <i>para</i>-position to −COOH lead to a variation of the photoelectrochemical properties, electronic transitions, and device performances. Characterization of the molecular structure, the electronic/optical properties of the dyes, as well as their photovoltaic performance in DSCs was accomplished by means of electrochemistry, quantum chemical methods, and various spectroscopic techniques such as photoinduced absorption, steady-state spectroscopy, and time-resolved transient absorption studies on femto- and nanosecond time scales. Thereby, significant dependence of DSCs performances on the substituents and anchoring groups was observed. In general, cyano substituents lead to improved DSCs performances. On the other hand, the insertion of an acetylene linker in combination with a cyano group does not enhance the device efficiencies. Devices composed of a <i>para</i>-cyano benzoic acid as anchor revealed maximum IPCE values of 80% with a PCE of 4.50% at AM 1.5 G illumination (100 mW cm^–2) due to retarded charge recombination dynamics