KuQuinones as sensitizers for NiO based p-type dye-sensitized solar cells

Abstract

A new series of KuQuinones (KuQs) have been synthesized and employed as dye-sensitizers for NiO-based p-type dye-sensitized solar cells (p-DSSCs). KuQs are pentacyclic quinoid compounds which are characterized by a fully conjugated structure that is responsible for the strong and broad absorption in the visible spectrum. The HOMO/LUMO states of KuQs considered here have matching energy levels with the upper edge of the NiO valence band and I−/I3− redox potential energy. These features render such compounds suitable for NiO sensitization in p-DSSCs. The new carboxylic acid-substituted KuQ derivatives proposed here differ in the length of the alkyl chain. The JV characteristic curves and the external quantum efficiency spectra have been recorded. The results showed that the performances of KuQ-sensitized cells were similar to that of the benchmark sensitizer erythrosine B (Ery B), despite the lack of electronic conjugation between the anchoring group and the light absorbing unit. This result led us to hypothesize that the photoinduced charge transfer between the excited KuQ dyes and the NiO electrode occurred through space and not via chemical bonds as it usually occurs in these systems. The mechanism of charge transfer through space has been supported by data from IR spectroscopy

Effect of Sodium Hydroxide Pretreatment of NiOx Cathodes on the Performance of Squaraine‐Sensitized p‐Type Dye‐Sensitized Solar Cells

“…Therefore, the synergic passivation effect created by a longer alkyl chain and the alkali pretreatment hamper the process of recombination between the unbound Ni(III) sites and iodide anions . The recombination resistance is directly proportional to the lifetime of the holes photoinjected in NiO x (compare trends of R rec and τ h in Tables 4 and 5), with R rec related to the cell parameter of open circuit potential . Since the insulating action of the O4 squaraines against photoinjection and charge recombination becomes more efficacious upon increase of alkyl chain size as testified by the increase of R t and R rec terms, the decrease of J SC / η with the increase of alkyl chain size is offset by the quasi‐constancy of the value of V OC (Table ).…”

“…The defective Ni(III) sites are mostly localized on the surface of the oxide and represent the sites of anchoring of the dye‐sensitizer by virtue of the strong electrophilic character which favours anion adsorption . Moreover, Ni(III) sites interact very strongly with the basic moiety ‐CO 2 − of the dye ,. Based on these findings, it is reasonable to assume that the reaction of nickel oxide with NaOH will mostly consist in the binding of the hydroxide anion to Ni(III) centres with consequent decrease of the surface sites actually available for dye‐anchoring.…”

“…It is found that the transport resistance of the photoelectrode ( R t values in the second column from left in Tables 3 and 4) decreases upon increase of the short circuit current density and conversion efficiency ( J SC and η values in Table ). Since R t is inversely proportional to the concentration of the charge carriers photoinjected in NiO x , and a relatively large value of J SC / η indicates a correspondingly high number of photoinjected charge carriers, it is expectable that R t decreases with J SC / η . Such a correlation between the ascending trend of J SC / η and the descending trend of R t holds also when NiO x cathode is treated with NaOH.…”

3,7‐Bis(N‐methyl‐N‐phenylamino)phenothiazinium Salt: Improved Synthesis and Aggregation Behavior in Solution

“…Furthermore, linking our experience in synthesis optimization [24][25][26][27][28][29][30][31] together with a broad investigation of literature data, we have also optimized a one-pot reaction, aimed to overcome the aforementioned synthetic troubles, thus improving the application of this class of compounds as dyes in the solar cells field, in the photodynamic therapy, likewise to study their interactions with DNA and proteins. [32] the π-stacked dimer of MB (Figure 1) converged to a minimum of energy, whereas the dimeric form of 1 did not.…”

Effect of Sensitization on the Electrochemical Properties of Nanostructured NiO

“…The optical [10][11][12][13][14]30,31], magnetic [32,33], electrochemical [34], and photoelectrochemical [35,36] properties of NiO (either in the bulk state or in the nanostructured version) are considerably altered when the surface of the oxide is dye-sensitized [37]. Such a type of electrode modification consists mainly in the impartation of additional optical absorption [38][39][40][41][42][43][44][45][46][47][48][49] and photoelectroactivity to NiO in the NIR-Vis range, i.e., in a spectral range of lower energies with 2 of 18 respect to the intrinsic optical absorption of pristine NiO (typically in the near ultraviolet (UV)) [50]. Dye sensitization of nanostructured p-type NiO is finalized principally to the realization of devices, such as dye-sensitized solar cells of p-type (p-DSCs) [51][52][53][54][55][56][57][58][59], light-fueled electrolyzers for hydrogen generation [5,[60][61][62][63][64][65], and photoelectrochemical reactors for carbon dioxide reduction …”