Porphyrins are major sensitizers in dye-sensitized solar cells (DSSC) results in very high power conversion efficiency, however, aggregation tendency and visible range absorption avoids realistic applications. Thus, designing of novel porphyrins based sensitizers are essential to resolve the current existing issues. In this context, seven D-π-A porphyrin dyes (LG1-LG7) engineered with 3ethynyl phenothiazine tethered at the meso-position and π-spacers such as 4-ethynyl phenyl (LG1), 5-efficiency in liquid electrolyte, which is very useful to make the efficient future generated dye sensitized solar cells.

In this paper, we present results from the detailed investigations on the synthesis, optical, emission, electrochemical, and ultrafast nonlinear optical (NLO) properties along with the excited state dynamics of zinc­(II) 2,10,16,24-tetrakis­(9-phenyl-9H-carbazol-2-yl)­phthalocyanine (CBZPC1) and zinc­(II) 2,10,16,24-tetrakis­(4-(9H-carbazol-9-yl)­phenyl)­phthalocyanine (CBZPC2). Due to the presence of carbazole moieties, the Soret band was found to be broadened. The emission studies performed using different solvents revealed the fluorescence yields in the range of 0.10–0.27 and the time-resolved fluorescence data revealed radiative lifetimes of, typically, a few nanoseconds. Femtosecond transient absorption measurements indicated the formation of triplet states within the first nanosecond of photoexcitation. From the cyclic voltametric studies, the oxidation and reduction processes were found to be ring centered. Spectral changes in the UV–visible absorption were recorded by means of spectro-electrochemical analysis at an applied potential. The DFT and TD-DFT analysis was employed using B3LYP hybrid functional theory and 6-31G­(d,p) basis set in the Gaussian 09 package. The NLO properties of CBZPC1 and CBZPC2 were investigated using the Z-scan technique and femtosecond (fs) pulses with kHz and MHz repetition rates. Closed and open aperture Z-scan data were recorded at three different wavelengths of 600, 700, and 800 nm, and the NLO coefficients were extracted from both types of data. Two-photon absorption (TPA) was the dominant mechanism observed in the open aperture Z-scan data. The real and imaginary parts of the χ(3) along with the two-photon absorption cross sections were evaluated. Our NLO data and large 2PA coefficients and cross sections obtained indicate the potential of these compounds for applications in optical limiting and optical switching applications.

A charge transport layer based on transition metal‐oxides prepared by an anhydrous sol–gel method normally requires high‐temperature annealing to achieve the desired quality. Although annealing is not a difficult process in the laboratory, it is definitely not a simple process in mass production, such as roll‐to‐roll, because of the inevitable long cooling step that follows. Therefore, the development of an annealing‐free solution‐processable metal‐oxide is essential for the large‐scale commercialization. In this work, a room‐temperature processable annealing‐free “aqueous” MoO x solution is developed and applied in non‐fullerene PBDB‐T‐2F:Y6 solar cells. By adjusting the concentration of water in the sol–gel route, an annealing‐free MoO x with excellent electrical properties is successfully developed. The PBDB‐T‐2F:Y6 solar cell with the general MoO x prepared by the anhydrous sol–gel method shows a low efficiency of 7.7% without annealing. If this anhydrous MoO x is annealed at 200 °C, the efficiency is recovered to 17.1%, which is a normal value typically observed in conventional structure PBDB‐T‐2F:Y6 solar cells. However, without any annealing process, the solar cell with aqueous MoO x exhibits comparable performance of 17.0%. In addition, the solar cell with annealing‐free aqueous MoO x exhibits better performance and stability without high‐temperature annealing compared to the solar cells with PEDOT:PSS.