Star-Shaped D–A Small Molecules Based on Diketopyrrolopyrrole and Triphenylamine for Efficient Solution-Processed Organic Solar Cells

Abstract

Three star-shaped D-A small molecules, (P-DPP)(3)TPA, (4-FP-DPP)(3)TPA, and (4-BuP-DPP)(3)TPA were designed and synthesized with triphenylamine (TPA) as the core, diketopyrrolopyrrole (DPP) as the arm, and unsubstituted or substituted benzene rings (phenyl, P; 4-fluoro-phenyl, 4-FP; 4-n-butyl-phenyl, 4-BuP) as the end-group. All the three small molecules show relatively narrow optical band gaps (1.68-1.72 eV) and low-lying highest occupied molecular orbital (HOMO) energy levels (-5.09∼-5.13 eV), implying that they are potentially good electron donors for organic solar cells (OSCs). Then, photovoltaic properties of the small molecules blended with [6,6]-phenyl-C(61)-butyric acid methyl ester (PC(61)BM) as electron acceptor were investigated. Among three small molecules, the OSC based on (P-DPP)(3)TPA:PCBM blend exhibits a best power conversion efficiency (PCE) of 2.98% with an open-circuit voltage (V(oc)) of 0.72 V, a short-circuit current density (J(sc)) of 7.94 mA/cm(2), and a fill factor (FF) of 52.2%, which may be ascribed to the highest hole mobility of (P-DPP)(3)TPA.

New acceptor–donor–acceptor-type conjugated molecules bearing naphtho[1,2-b:5,6-b′]dithiophene and (E)-1,2-di(thiophen-2-yl)ethene and their applications in thin-film transistors and photovoltaic cells

“…The spectra of TVT(DPP) 2 and NDT (DPP) 2 display strong absorption bands in the long wavelength range because of intramolecular charge transfer between the donor and acceptor units in the SMs and weak absorption bands in the short wavelength region attributed to the p-p transition of the isolated p-conjugated molecules. It was found that such absorption spectra are similar to those of typical donor-acceptor-type conjugated molecules [27]. While the maximum absorption wavelength (l max ) of TVT(DPP) 2 in solution is at 621 nm, the l max of its film is red-shifted to 627 nm with a shoulder at 700 nm, which was attributed to stronger intermolecular interactions in the solid state.…”

Donor Materials for Organic Solar Cell (OSC)

“…All these three SMs (SM14) showed relatively narrow optical band gaps (1.68−1.72 eV) and low-lying HOMO energy levels. With the similar physical properties, OSCs based on SM14-1:PC 61 BM blend exhibited the best PCE of 2.98 %, which may be ascribed to its highest hole mobility among these three molecules [136]. Very recently, Zhan's utilized the fused IDT as the donor to build the DPP-based linear acceptor-donoracceptor molecule (SM15), which displayed bipolar properties in the OPV system.…”

Peripheral group effects on the photophysical and photovoltaic properties of bulk-heterojunction type solar cells based on star-shaped conjugate molecules with triphenylamine core

“…To avoid recombination of excitons, the P/N heterojunction phase must be controlled at the nanoscale level [42,43]. We used AFM to investigate the compatibility and morphology of our conjugated SSM/PC 61 BM composite films [33,44]. Figs.…”