Molecular engineering of new phenothiazine-based D–A–π–A dyes for dye-sensitized solar cells

Abstract

We report new D–A–π–A dyes gained by molecular engineering for DSSCs, achieving a highest photoelectric conversion efficiency of 6.35%.

Electronic and optical properties’ tuning of phenoxazine-based D-A2-π-A1 organic dyes for dye-sensitized solar cells. DFT/TDDFT investigations

“…Researches have shown that the DSSCs based on metal-complex sensitizers exhibit slightly higher efficiency than those of metal-free organic sensitizers [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. However, the metal-complex sensitizers have limited resources, low molar extinction coefficient and high cost, which limit their industrial applications [ 12 , 14 ]. Studies have revealed that metal-free organic sensitizers provide better performance than metal complexes' sensitizers because of higher molar extinction coefficients, tunable spectral responses, ease of production and availability [ 9 , 10 , 13 , 15 ].…”

“…Many metal-free organic dyes including phenothiazine [ 14 ], carbazoles, coumarin, triarylamines, triphenylamine [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ], or phenoxazine [ 24 , 25 , 26 , 27 ] have been designed and synthesized and found to possess promising properties that can enhance photovoltaic performances better than most prominent metal complex dyes. In recent times, phenoxazine has shown preference as an electron-donating moiety.…”

“…Higher oxidation potential and lower aromatic energy of furan as π-spacer has been reported to aid stability of the dye and improve power conversion efficiency [ 30 ] amongst many other π-spacers such as pyrrole, thiazole, benzene or thiophene used in the study of organic dyes [ 14 , 25 , 31 ]. According to Buene and co-workers [ 32 ], furan π-spacer performed better than popular π -spacers such as thiophene and phenyl, therefore the use of furan as π-spacer is encouraged to facilitate intramolecular charge transfer from donor to acceptor [ 14 ]. The acceptor group can perform the function of an electron trap and also an anchor group [ 14 , 15 , 25 , 27 ].…”

“…According to Buene and co-workers [ 32 ], furan π-spacer performed better than popular π -spacers such as thiophene and phenyl, therefore the use of furan as π-spacer is encouraged to facilitate intramolecular charge transfer from donor to acceptor [ 14 ]. The acceptor group can perform the function of an electron trap and also an anchor group [ 14 , 15 , 25 , 27 ]. Cyanoacrylic acid is regarded as an excellent electron acceptor owing to its excellent electron withdrawing ability [ 33 ] compared to various reported acceptor groups such as benzothiadiazole or 2-cyano-2-pyran-4-ylidene-acetic acid [ 14 , 30 ].…”

Substituted and Anchoring Groups Improve the Efficiency of Dye-Sensitized Solar Cells

“…Alkyl and alkoxy chains are known as accessary groups in the architecture of both electron donors and π‐bridges to prohibit the π‐π aggregation of dyes on the TiO 2 surface . Synchronously, the alkoxy chains can play the roles of electron‐donors . As is well known, the typical YD2‐ o ‐C8 dye displays better photovoltaic performance than YD2 dye in their DSC devices owing to its additional octyloxy groups …”