Effect of Nitrogen Cation as “Electron Trap” at π-Linker on Properties for p-Type Photosensitizers: DFT Study

Abstract

On the basis of thieno(3,2-b)thiophene and dithieno[3,2-b:2′,3′-d]thiophene (T2 and T3 moieties) as π-linker, the A, D and S series dyes were designed to investigate the effect of the introducing N+ as an “electron trap” into T2 and T3 on the properties of the dyes. The optimized structures, electronic and optical properties were investigated by the density functional theory (DFT) and time-dependent DFT (TD-DFT). The results show that the properties of the dyes are sensitive to the N+ position in π-linkers. D series dyes with electron-withdrawing units located near the donor have better properties than the corresponding A series with the electron-withdrawing units located near the acceptor. For A and D series, the N+ modified dye named T2N+1-d displays the largest red shift of the UV–vis absorption, the maximum integral values of the adsorption-wavelength curves over the visible light, the highest light harvesting efficiency (LHE, 0.996), and the strongest adsorption energy (−44.33 kcal/mol). T2N+1-d also has a large driving force of hole injection (ΔGinj, −0.74 eV), which results in a more efficient hole injection. Bearing a lengthier π-linker than T2N+1-d, the properties of T2N+1-s are further improved. T2N+1-d moiety or its increased conjugated derivatives may be a promising π-linker.

Design of high performance p-type sensitizers with pyridinium derivatives as the acceptor by theoretical calculations

“…The structures of the dye/ NiO system were optimized at the GGA-PBE/DN level under acetonitrile as the solvent, using the Dmol 3 program of Materials Studio 6.0. 18,19 The adsorption energies between the dye and the NiO surface were calculated at the same level.…”

“…41 In general, the value of the adsorption energy for the dye/NiO system determines the strength of the interaction between the dye and the surface of NiO semiconductor. 19 A large adsorption energy can lead to a strong electronic coupling between the anchoring unit of the dye and the NiO surface, which can also increase the hole transfer rate. 41 To calculate the adsorption energies, a nickel oxide cluster with three layers of 12 Â 3 NiO were established, and the (NiO) 12Â3 cluster was optimized at the GGA-PBE/DN level under a acetonitrile solvation model, using the Dmol 3 program.…”

The solvent effect on a styryl‐bodipy derivative functioning as an AND molecular logic gate

“…Such changes can be related to the operation of fluorescence chemosensors, molecular switches, and logic gates (via the familiar Boolean logic where the modulators correspond to the inputs and the observed changes correspond to the outputs) . As a consequence, the field of molecular logic gates and generally of chemosensors and molecular switches is very active and many research groups around the world work on these subjects …”

“…The majority of fluorescence chemosensors and molecular switches are based on the “on‐off” or “off‐on” response of photoinduced electron transfer (PET), because PET produces very sharp changes in the signal intensity and it can be modulated in such a way as to generate significant changes in the emission wavelengths. The impact of PET on UV‐vis absorption is often negligible and other effects, such as intramolecular charge transfer (ICT) could affect the UV‐vis absorption . Finally, it should be noted that there are also fluorescent switches which are not built based on PET, but on other mechanisms, such as twisted intramolecular charge transfer …”