Two novel near‐infrared (NIR)‐sensitive unsymmetrical squaraine dyes, SQ‐258 and SQ‐259, for their suitability as a sensitizer in dye‐sensitized solar cells (DSSCs) are designed and synthesized, followed by photophysical and photovoltaic characterizations. It is demonstrated that introducing a 1,3‐indandione acceptor unit in the central squaric acid core of SQ‐259 leads to the suppression of dye aggregation owing to its nonplanar molecular geometry and the broadening of the optical absorption and photon‐harvesting window up to 800 nm. Owing to the extended wavelength photon harvesting, SQ‐259 improves the photoconversion efficiency (PCE) compared to its SQ‐258 dye counterpart. However, despite its wide wavelength photon harvesting, the improvement in the PCE of SQ‐259 is less pronounced, and this is attributed to the small driving force for injection of electrons (0.29 eV), hampered electronic coupling, and decreased electron lifetime for resistance to recombination (7.9 ms), which is confirmed by the cyclic voltammetry, quantum chemical calculation, and electrochemical impedance spectroscopic investigations, respectively.

Bifacial solar cells (BFSCs) are gaining popularity due to their compactness, space‐saving property, and higher photoconversion efficiency (PCE) than mono‐facial solar cells. Bifacial dye‐sensitized solar cells (BF‐DSSCs) are fabricated and characterized utilizing D‐205 as a dye‐sensitizer in combination with I‐/I3 ‐ and Co2+/Co3+ redox electrolytes. BF‐DSSCs using iodine‐based electrolytes demonstrate a cumulative PCE and bifaciality factor (BFF) of 13.05% and 85%, respectively. The hampered PCE under back‐side light illumination is attributed to the absorption of photons by the electrolyte itself. Contrary to this, BF‐DSSCs fabricated using cobalt‐complex‐based redox electrolyte exhibits an exceptionally high BFF of nearly 100% with a PCE of 4.77% and 4.75% under the front and rear light illumination, respectively. Although the open circuit voltage (Voc) of the BF‐DSSCs fabricated using cobalt electrolyte (with deeper redox potential) is slightly higher than that of BF‐DSSCs fabricated using iodine electrolyte, their cumulative PCE (9.52%) is much lower than that of iodine‐based device counterparts (13.05%). This decrease in PCE is attributed to the relatively fast charge recombination in the cobalt electrolyte‐based BF‐DSSCs.This article is protected by copyright. All rights reserved.

Fabrication of uniform and oriented thin films of conjugated polymers (CPs) with controlled thickness is essential for the implementation of organic devices. Over the years, unidirectional floating film transfer method (UFTM) has emerged as a facile technique for the fabrication of oriented thin films but its distribution of orientation in vertical (thickness) direction has not been explored yet. To investigate this, thin films of nonregioregular poly(3‐hexylthiophene) are fabricated using UFTM with different concentrations of CPs to obtain thickness variation from 11 to 47 nm. Thin films of 4% and 9% polymer solution have similar dichroic ratio of 5.5 but have an appreciable difference in film thickness of 12 and 47 nm where thicker films are disordered as probed by polarized absorption spectra. Organic field‐effect transistors fabricated using thinner films (12 nm) exhibit a saturated charge carrier mobility of 2.3 × 10−3cm2 V−1 s−1, an order of magnitude higher than its thicker (47 nm) counterpart. This difference in device performance can be attributed to the fact that charge transport is principally governed by the top polymer surface at air–polymer interface, which is found to be more disordered owing to the vertical distribution of orientation.