14.2% Efficiency Dye‐Sensitized Solar Cells by Co‐sensitizing Novel Thieno[3,2‐b]indole‐Based Organic Dyes with a Promising Porphyrin Sensitizer

Abstract

A new series of 4-hexyl-4H-thieno[3,2-b]indole (HxTI) based organic chromophores is developed by structural engineering of the electron donor (D) group in the D-HxTI-benzothiadiazole-phenyl-acceptor platform with different fluorenyl moieties, such as unsubstituted fluorenyl (SGT-146) and hexyloxy (SGT-147), decyloxy (SGT-148) and hexyloxy-phenyl substituted (SGT-149) fluorenyl moieties. In comparison to a reference dye SGT-137 with a biphenyl-based donor, the effects of the donating ability and bulkiness of the fluorenyl based donor in this D-π-A-structured platform on molecular properties and photovoltaic performance are investigated to establish the structure-property relationship. The photovoltaic performance of dye-sensitized solar cells (DSSCs) is improved according to the bulkiness of the donor groups. As a result, the DSSCs based on SGT-149 show high power conversion efficiencies (PCEs) of 11.7% and 10.0% with a [Co(bpy) 3 ] 2+/3+ (bpy = 2,2′-bipyridine) and an I − /I 3 − redox electrolyte, respectively. Notably, the co-sensitization of SGT-149 with a SGT-021 porphyrin dye by utilizing a simple "cocktail" method, exhibit state-of-the-art PCEs of 14.2% and 11.6% with a [Co(bpy) 3 ] 2+/3+ and an I − /I 3 − redox electrolyte, respectively.

Benzothiadiazole-based photosensitizers for efficient and stable dye-sensitized solar cells and 8.7% efficiency semi-transparent mini-modules

“…48 Using a convenient strategy referred to as "dye cocktails" for the photosensitization, state-of-the-art PCEs of 14.2% and 11.6% with a [Co(bpy) 3 ] 2+ / 3+ and an I À /I 3 À redox electrolyte respectively, have been reported in 2020. 15 The co-graing onto the TiO 2 surface of two properly designed organic dyes affords a compact and robust self-assembled monolayer, 17 which results in a reduction of interfacial charge recombination and an improvement of the V oc . Following this strategy, we combined YKP-88 and YKP-137, two dyes just differing from the alkoxy-chains on the TPA unit, to cosensitize TiO 2 mesoporous electrodes.…”

“…Nowadays they appear to be adapted to solve some of these drawbacks. 10 In terms of power conversion efficiencies (PCEs), the best DSSCs performances lie in the range of 10 to 14.2%, [11][12][13][14][15] which is lower compared to BHJ and PSC, but interestingly they already demonstrated superior long-term stability. Indeed, when non-volatile electrolytes are employed, [16][17][18] their performance can be conserved under harsh testing conditions, 16 and a stability corresponding to approximately 10 years of use in real conditions has been demonstrated.…”

Comparative Studies on the Structure–Performance Relationships of Phenothiazine-Based Organic Dyes for Dye-Sensitized Solar Cells

“… 22 Recently, Kim et al have also shown a striking PCE of 14.2% by co-sensitizing novel thieno-[3,2-b]indole-based organic dye and a porphyrin sensitizer. 23 …”

Complexity of Electron Injection Dynamics and Light Soaking Effects in Efficient Dyes for Modern DSSC

“…Thanks to the advances in new compounds and materials design, the highest achieved PCEs has been pushed up to~14% [16,17] at full sunlight and 32-34% [5,18] in ambient light conditions. At the same time, the above-mentioned advances have raised fundamental questions on the operation of systems comprising the state-of-the-art cell components.…”

“…In particular, no detailed information has been published on the examination of the excited state dynamics of Y123 interacting with mesoporous titania in broad visible light spectrum. This issue should be examined, especially in light of recent advances on new, more complex and highly efficient TPA dyes [17,[22][23][24]. It is especially important to establish whether the dynamics of electron injection in the fully operating solar cells occurs on the ultrafast time scale up to single ps (like for many organic dyes for DSSC), or extends into much longer time scales, e.g., for some ruthenium compounds [25,26].…”