Since the discovery of graphene in the early 2000′s, polycyclic aromatic hydrocarbons (PAHs) have been resurrected and new synthetic tools have been developed to prepare unprecedented structures with unique properties. One application that has been overlooked for this class of molecules is organic solar cells (OSCs). In this account, we present the recent development in the preparation of moderate to low band gap PAHs that could potentially be used as semiconducting materials in OSCs. Our focus is directed toward all‐carbon PAHs as well as their polymeric analogs.

The motion of CH3NH3+ cations in the low-temperature phase of the promising photovoltaic material methylammonium lead triiodide (CH3NH3PbI3) is investigated experimentally as well as theoretically, with a particular focus on the activation energy. Inelastic and quasi-elastic neutron scattering measurements reveal an activation energy of ∼48 meV. Through a combination of experiments and first-principles calculations, we attribute this activation energy to the relative rotation of CH3 against an NH3 group that stays bound to the inorganic cage. The inclusion of nuclear quantum effects through path integral molecular dynamics gives an activation energy of ∼42 meV, in good agreement with the neutron scattering experiments. For deuterated samples (CD3NH3PbI3), both theory and experiment observe a higher activation energy for the rotation of CD3 against NH3, which results from the smaller nuclear quantum effects in CD3. The rotation of the NH3 group, which is bound to the inorganic cage via strong hydrogen bonding, is unlikely to occur at low temperatures due to its high energy barrier of ∼120 meV.

Understanding doping mechanisms is essential for optimizing the doping efficiency and rationally designing next generations of dopants and organic materials. Over the last years, N-DMBI became a reference solution-processed n-type dopant, affording decent air-stability and record power factor for thermoelectric energy generation. Nevertheless, a complete

New benzothiadiazole-based dyes are synthesized, characterized and used for the fabrication of robust and efficient solar cells and mini-modules.

We report the synthesis of π-extended ullazine derivatives annulated with either electron-poor pyridine or electron-rich thiophene units through a metal-free, photochemical cyclodehydrochlorination (CDHC) reaction.

3D inverse opal (3D-IO) oxides are very appealing nanostructures to be integrated into the photoelectrodes of dye-sensitized solar cells (DSSCs). Due to their periodic interconnected pore network with a high pore volume fraction, they facilitate electrolyte infiltration and enhance light scattering. Nonetheless, preparing 3D-IO structures directly on nonflat DSSC electrodes is challenging. Herein, 3D-IO TiO 2 structures are prepared by templating with self-assembled polymethyl methacrylate spheres on glass substrates, impregnation with a mixed TiO 2 :SiO 2 precursor and calcination. The specific surface increases from 20.9 to 30.7 m 2 g −1 after SiO 2 removal via etching, which leads to the formation of mesopores. The obtained nanostructures are scraped from the substrate, processed as a paste, and deposited on photoelectrodes containing a mesoporous TiO 2 layer. This procedure maintains locally the 3D-IO order. When sensitized with the novel benzothiadiazole dye YKP-88, DSSCs containing the modified photoelectrodes exhibit an efficiency of 10.35% versus 9.26% for the same devices with conventional photoelectrodes. Similarly, using the ruthenium dye N719 as sensitizer an efficiency increase from 5.31% to 6.23% is obtained. These improvements originate mainly from an increase in the photocurrent density, which is attributed to an enhanced dye loading obtained with the mesoporous 3D-IO structures due to SiO 2 removal.

A π-conjugated copolymer based on a pyrene diimide unit (P(PyDI-T2)) was synthesized using the Suzuki−Miyaura crosscoupling reaction between 4,5,9,10-pyrene diimide-2,7-diboronic ester and 2,2′-dibromo-5,5′-bithiophene for use as an active material in a Li-ion battery. Usually, diimide molecules are known to demonstrate reversible redox processes with a maximum of a two-electron insertion per unit. The unique structure of pyrene diimide, consisting of a pyrene core bearing two imide functions lying on formal double bonds, was anticipated to potentially demonstrate reversible redox processes involving four electrons per unit via aromatic stabilization. Also, the 2-and 7-positions are much less sterically hindered than similar relative positions in other diimides and hence should permit good electron mobility in the resulting polymer. Unfortunately, we were unable to observe any reduction phenomena in a half-cell (with a Li anode), likely due to negligible electronic conductivity. Subsequently, P(PyDI-T2) was blended with SWCNTs for dispersion in order to enhance both conductivity and surface area. High concentration dispersion was filtered to obtain a freestanding film of P(PyDI-T2)/SWCNT, with an intrinsic conductivity of 30 S/cm, which was used directly as a cathode in the half-cell. Reversible redox pointing to two one-electron phenomena was observed with 40.6 mA h/g at a galvanostatic slow rate of C/50 with a high mass loading of 3.2 mg/cm 2 . Density functional theory calculations were performed on pyrene diimide units to elucidate poor mobility and to compare Gibbs free energies for the second reduction of each site.

Linear and helical graphene nanoribbons (L-PyGNR and H-PyGNR) bearing electron-rich pyrrole units have been synthesized by using the photochemical cyclodehydrochlorination (CDHC) reaction. The pyrrole units in the polymer backbone make the polymer electron-rich with moderate bandgap values and relatively high HOMO energy levels. The planarization of the pyrrole unit through cyclization yields a bandgap value almost 0.5 eV lower than that measured for polypyrrole. Conductivity values in the thin film up to 0.12 S/cm were measured for the chemically oxidized L-PyGNR (four-point method). Both GNRs showed excellent fluorescence sensing properties for TNT in solution with K SV values up to 6.4 × 10 6 M −1 .