A New Series of EDOT Based Co-Sensitizers for Enhanced Efficiency of Cocktail DSSC: A Comparative Study of Two Different Anchoring Groups

Abstract

Herein, we report the design and synthesis strategy of a new class of five EDOT based co-sensitizers (CSGR1-5) by introducing different donors (2,3,4-trimethoxypheny, 2,4-dibutoxyphenyl, and 2,4-difluorophenyl) and anchoring groups (rhodamine-3-acetic acid and cyanoacetic acid) systematically. The synthesized metal-free organic co-sensitizers were employed for cocktail dye-sensitized solar cells along with N749 (black dye). The DSSC devices with a mixture of co-sensitizers (CSGR1-5) and N749 have shown a 7.95%, 8.40%, 7.81%, 6.56% and 6.99% power conversion efficiency (PCE) respectively, which was more than that of single N749 dye PCE (6.18%). Enhanced efficiency could be ascribed to the increased short circuit current (J sc ) and open circuit voltage (V oc ). The increased J sc was achieved due to enhanced light harvesting nature of N749 device upon co-sensitization with CSGR dyes and feasible energy levels of both the dyes. The V oc was improved due to better surface coverage which helps in decreasing the rate of recombination. The detailed optical and electrochemical properties were investigated and complimented with theoretical studies (DFT).

Co-Sensitization Effects of Indoline and Carbazole Dyes in Solar Cells and Their Neutral–Anion Equilibrium in Solution

“…The long alkyl chain of JH-1 inhibited electron recombination, and the complementary spectral response in the co-sensitized device affected the efficiency of the entire device [ 10 ]. A positive effect of co-sensitization has been also demonstrated for DSSC systems in which one of the dyes was based on ruthenium [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. The advantages of co-sensitization, such as improvement of optical absorption, IPCE response, electron lifetime, dye regeneration, dye coverage and cell preparation cost, have been demonstrated for DSSC cells sensitized with the dyes of the structures D-A-π-A and π-A in combination with a copper-based electrolyte [ 21 ].…”

Efficiency enhancement of ruthenium-based DSSCs employing A–π–D–π–A organic Co-sensitizers

“…The large or midfrequency region signies the recombination resistance (R 2 ) at the working electrode of the TiO 2 /dye/electrolyte interface. 27,46 The third semicircle (low-frequency range) indicates the series resistance (R 1 ) of platinum and FTO glass. The obtained recombination resistance values (R 2 ) of the DSSCs sensitized In fact, the higher the R 2 value, the lower the charge recombination rate between the conduction band of the TiO 2 semiconductor and the electrolyte.…”

“…The improved V OC observed for the co-sensitized DSSC devices can be attributed to the lower rate of recombination between the injected electrons in the TiO 2 semiconductor conduction band and the redox electrolyte (I 3 À /I À ). Owing to their small size, the co-sensitizers provide better surface coverage 27,45 by adsorbing into the pores and gaps in the TiO 2 , whereas the steric hindrance of the bulky ruthenium-based dye molecule prevents its adsorption. From the results, the lower efficiency of IMA5 when co-sensitized with IMA1 (h ¼ 5.44%) and IMA4 (h ¼ 5.83%) compared to when cosensitized with IMA2 (h ¼ 6.25%) and IMA3 (h ¼ 6.19%) can be attributed to the breaking of the continuous conjugation by the pyrazole moiety in IMA1 and by the thiazole moiety in the case of IMA4, which would prevent efficient electron injection into the conduction band of TiO 2 .…”

“…1,25 Actually, co-sensitization of DSSCs signicantly increases the performance of photovoltaics compared to a single sensitizer. [26][27][28] This is attributed to preventing the aggregation of the dye and minimizing charge recombination, increasing the efficient accumulation of both types of dyes on the TiO 2 surface owing to the difference in the molecular sizes of the dyes, thus facilitating the harvesting of a maximum number of incident photons by the cell. 29 Different organic push-pull sensitizers have been used in DSSCs as effective co-sensitizers for Ru(II) complexes compared to individual dye cells; for example, a black dye increased photocurrent efficiency (PCE) by up to 11% when co-sensitized with D131 color dye, 30 N3 dye when cosensitized with simple aniline-based D-A architecture enhanced the PCE by up to 7.02%, 1 Ru sensitizer (SPS-01) co-sensitization with a metal-free dye containing thienyluorene (JD1) increased the PCE by 8.30% (ref.…”

Efficiency enhancement of natural cocktail dyes in a TiO2-based dye-sensitized solar cell and performance of electron kinetics on the TiO2 surface

“…Zolkepli et al (2015) showed that the 1:4 mixture of Tradescantia spathacia and Ixora coccinea pigments had the highest cell efficiency (= 0.80%). Koyyada et al (2019) systematically introduced alternative donors and anchoring groups, and we created a new class of five EDOT-based co-sensitizers with N749 (black dye). The power conversion efficiency (PCE) of DSSC devices with a mixture of co-sensitizers and N749 was the maximum, which was higher than the PCE of a single N749 dye (6.18%).…”