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Low‐Recombination Thieno[3,4‐b]thiophene‐Based Photosensitizers for Dye‐Sensitized Solar Cells with Panchromatic Photoresponses
Author(s) -
Brogdon Phillip,
Cheema Hammad,
Delcamp Jared H.
Publication year - 2017
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201701259
Subject(s) - thiophene , absorbance , dye sensitized solar cell , photochemistry , energy conversion efficiency , chemistry , alkyl , absorption (acoustics) , cyclic voltammetry , band gap , absorption spectroscopy , density functional theory , open circuit voltage , materials science , optoelectronics , electrochemistry , organic chemistry , optics , electrode , computational chemistry , voltage , physics , chromatography , quantum mechanics , electrolyte , composite material
We report four NIR photosensitizers employing a low‐recombination donor and a thieno[3,4‐b]thiophene (3,4‐TT) π bridge for use in dye‐sensitized solar cells. The inclusion of electron rich π spacers red‐shifts the dye absorbance with solution absorption onsets reaching 700 nm. Dyes were found to have suitable energy levels for rapid electron transfers using cyclic voltammetry and UV/Vis–NIR absorption spectroscopy. Computationally optimized ground‐state geometries show an increased torsional angle between π spacer and π bridge brought about by an added alkyl chain. This results in a widened optical band gap and increased oxidation potentials owing to a weakening of the electron‐accepting ability of 3,4‐TT for solution‐state measurements. Interestingly in terms of device parameters, the alkylated π spacer had a nearly identical incident photon‐to‐current conversion efficiency (IPCE) curve onset when compared to a non‐alkylated analogue, suggesting more similar dye geometries on the surface of TiO 2 . Elevated short‐circuit current density ( J SC ) values and comparable open‐circuit voltage ( V OC ) values were observed in the alkylated‐π‐spacer‐dye‐based devices with power conversion efficiencies up to 6.8 % observed with IPCE onsets exceeding 800 nm.