In this work, we study the performance of organic photovoltaic (OPV) cells based on the PTB7:PC ₇₁ BM blend and the use of an alternative metal cathode called field's metal (FM) (Bi/In/Sn: 32.5%, 51%, 16.5%), which can be easily deposited through a vacuum-free process at regular atmosphere and low temperature (90 °C). The charge extraction and losses involved with the use of FM, in combination with an electron extraction layer, in this case the widely used polymer PFN, were fully analyzed using equivalent circuit models for the architecture ITO/PEDOT:PSS/PTB7:PC ₇₁ BM/PFN/FM. Power conversion efficiencies (PCEs) higher than 6% were reached with this architecture, which exhibited J _sc of 14.3 mA/cm ² , V _oc of 0.76 V, and FF of 0.6. The single-diode equivalent circuit model demonstrates that devices comprising FM as counterelectrode are characterized by a low series resistance (1.0 Ω · cm ² ), large shunt resistance (1.1 × 10 ⁵ Ω · cm ² ), and low saturation current (1.4 × 10 ^-7 mA/cm ² ). Additional electrical characterization, through impedance spectroscopy, was also carried out. The obtained PV parameters are similar to those exhibited by devices comprising standard counterelectrodes, i.e., Al, deposited through a high-vacuum evaporation process. Thus, FM, as nonconventional and alternative counterelectrode, in combination with an electron extraction layer, can be used to fabricate OPVs cells with very acceptable performance through a vacuum-free process.

We report single crystal X-ray diffraction (hereafter, SCXRD) analyses of derivatives featuring the electron-donor N-ethylcarbazole or the (4-diphenylamino)phenyl moieties associated with a -CN group attached to a double bond. The compounds are (2Z)-3-(4-(diphenylamino)-phenyl)-2-(pyridin-3-yl)prop-2-enenitrile (I), (2Z)-3-(4-(diphenylamino)phenyl)-2-(pyridin-4-yl)-prop-2-enenitrile (II) and (2Z)-3-(9-ethyl-9H-carbazol-3-yl)-2-(pyridin-2-yl)enenitrile (III). SCXRD analyses reveal that I and III crystallize in the monoclinic space groups P2/c with Z’ = 2 and C2/c with Z’ = 1, respectively. Compound II crystallized in the orthorhombic space group Pbcn with Z’ = 1. The molecular packing analysis was conducted to examine the pyridine core effect, depending on the ortho, meta- and para-positions of the nitrogen atom, with respect to the optical properties and number of independent molecules (Z’). It is found that the double bond bearing a diphenylamino moiety introduced properties to exhibit a strong π-π-interaction in the solid state. The compounds were examined to evaluate the effects of solvent polarity, the role of the molecular structure, and the molecular interactions on their self-assembly behaviors. Compound I crystallized with a cell with two conformers, anti and syn, due to interaction with solvent. DFT calculations indicated the anti and syn structures of I are energetically stable (less than 1 eV). Also electrochemical and photophysical properties of the compounds were investigated, as well as the determination of optimization calculations in gas and different solvent (chloroform, cyclohexane, methanol, ethanol, tetrahydrofuran, dichloromethane and dimethyl sulfoxide) in the Gaussian09 program. The effect of solvent by PCM method was also investigated. The frontier HOMO and LUMO energies and gap energies are reported.