Star-shaped Electron Acceptor Research Articles

Subphthalocyanine-Diketopyrrolopyrrole Conjugates: 3D Star-Shaped Systems as Non-Fullerene Acceptors in Polymer Solar Cells with High Open-Circuit Voltage.

Four star-shaped electron acceptors (C1 -OPh, C3 -OPh, C1 -Cl and C3 -Cl) based on a subphthalocyanine core bearing three diketopyrrolopyrrole wings linked by an acetylene bridge have been synthesized. These derivatives feature two different axial substituents (i. e., 4-tert-butylphenoxy (OPh) or chlorine (Cl)) and for each of them, both the C1 and the C3 regioisomers have been investigated. The four compounds exhibit a broad absorption band in the 450-700 nm region, with bandgap values near to 2 eV. These materials were applied in the active layer of inverted bulk-heterojunction polymer solar cells in combination with the donor polymer PBDB-T. Derivatives bearing the OPh axial group showed the best performances, with C1 -OPh being the most promising with a PCE of 3.27 % and a Voc as high as 1.17 V. Despite presenting the widest absorption range, the photovoltaic results obtained with C1 -Cl turned out to be the lowest (PCE=1.01 %).

Designing of non-fullerene 3D star-shaped acceptors for organic solar cells.

The design and fabrication of solar cells have recently witnessed the exploration of non-fullerene-based acceptor molecules for higher efficiency. In this study, the optical and electronic properties of four new three-dimensional (3D) star-shaped acceptor molecules (M1, M2, M3, and M4) are evaluated for use as acceptor molecules in organic solar cells. These molecules contain a triphenylamine donor core with diketopyrrolopyrrole acceptor arms linked via a thiophene bridge unit. Molecules M1-M4 are characterized by different end-capped acceptor moieties, including 2-(5-methylene-6-oxo-5,6-dihydrocyclopenta-b-thiophen-4-ylidene)malononitrile (M1), 2-(2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (M2), 2-(5-methyl-2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (M3), and 3-methyl-5-methylnene-thioxothiazolidin-4-one (M4). The properties of the newly designed molecules were compared with a well-known reference compound R, which was recently reported as an excellent acceptor molecule for organic solar cells. Molecules M1-M4 exhibit suitable frontier molecular orbital patterns for charge mobility. M2 shows maximum absorption (λmax) at 846.8nm in dichloromethane solvent, which is ideal for the design of transparent solar cells. A strong electron withdrawing end-capped acceptor causes a red shift in absorption spectra. All molecules are excellent for hole mobility due to a lower value of λh compared to the reference R. Graphical abstract Here, we have designed four new triphenylamine-based three-dimensional star-shaped electron acceptors with different electron withdrawing end-capped acceptor moieties, namely M1, M2, M3, and M4) for opto-electronic properties of organic solar cells. The designed star-shaped acceptor molecules show excellent optoelectronic properties with respect to reference compound R.

Star-shaped small molecule acceptors with a subphthalocyanine core for solution-processed non-fullerene solar cells

Two star-shaped electron acceptors (STIC and STFIC) based on subphthalocyanine (SubPc) as core and 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC) or 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (2FIC) as end groups, have been designed and synthesized. Both two acceptors show unique photophysical properties different from those of traditional SubPc based non-fullerene acceptors (NFAs): first, two strong absorption bands in the region of 400–700 nm with high extinction coefficients are observed; second, their spectra in films exhibit full width at half maximum (FWHM) over 260 nm, more than two-fold larger than those of traditional SubPc based NFAs; third, their optical bandgaps are around 1.6 eV, among the narrowest bandgaps for SubPc-based NFAs. Compared with STFIC with 2FIC end groups, the higher-lying lowest unoccupied molecular orbital (LUMO) level of STIC with IC end groups leads to the higher values of open circuit voltage (VOC) and power conversion efficiency (PCE) in organic solar cells (OSCs). Using PBDB-T as donor, the PCEs of 4.69% and 3.80% are achieved by OSCs based on STIC and STFIC, respectively. The PCE of 4.69% is also among the highest PCE values for SubPc-based solution-processed BHJ OSCs.

Subphthalocyanine-cored star-shaped electron acceptors with perylene diimide wings for non-fullerene solar cells

Two star-shaped electron acceptors with different linkages between the subphthalocyanine core and perylene diimide wings exhibit different molecular geometries, optical properties, energy levels and stacking behaviors, leading to different photovoltaic performances.

Star-Shaped Electron Acceptor based on Naphthalenediimide-Porphyrin for Non-Fullerene Organic Solar Cells

Star-Shaped Electron Acceptor based on Naphthalenediimide-Porphyrin for Non-Fullerene Organic Solar Cells

Star-shaped electron acceptors containing a truxene core for non-fullerene solar cells

Abstract A series of new electron acceptors containing a truxene core with intense optical absorption were synthesized and used for non-fullerene organic solar cells. Due to the weak electron-donating characteristic of truxene core and thereby weak intramolecular charge transfer interaction from electron-donating core to electron-withdrawing end groups, the resulting new acceptors show relatively wide optical band-gap and high-lying lowest unoccupied molecular orbitals (LUMOs), which consequently lead to complementary light spectra with narrow band-gap donor polymers and high open circuit voltage (Voc) in solar cells. Particularly, Tr(Hex)6-3BR, a star-shaped planar acceptor, produced the highest power conversion efficiency of 2.1% with a high Voc of 1.02 V when blended with PTB7-Th.

A near-infrared porphyrin-based electron acceptor for non-fullerene organic solar cells

In this work, a new star-shaped electron acceptor based on porphyrin as core, rhodanine and benzothiadiazole as end groups, was developed for non-fullerene solar cells. The molecule shows three distinct absorption regions due to the Soret and Q-bands of the porphyrin and the intramolecular charge transfer in the molecule. This molecule as electron acceptor was applied into non-fullerene solar cells by using a diketopyrrolopyrrole-based conjugated polymer as electron donor. An initial PCE of 1.9% was achieved with a broad photo-response from 300–850nm. The results demonstrate that porphyrin can be used to design near-infrared electron acceptors for organic solar cells.

An Electron Acceptor with Porphyrin and Perylene Bisimides for Efficient Non‐Fullerene Solar Cells

A star-shaped electron acceptor based on porphyrin as a core and perylene bisimide as end groups was constructed for application in non-fullerene organic solar cells. The new conjugated molecule exhibits aligned energy levels, good electron mobility, and complementary absorption with a donor polymer. These advantages facilitate a high power conversion efficiency of 7.4 % in non-fullerene solar cells, which represents the highest photovoltaic performance based on porphyrin derivatives as the acceptor.

A star-shaped electron acceptor based on 5,5′-bibenzothiadiazole for solution processed solar cells

A novel star-shaped molecule based on triphenylamine as the core and 5,5-bibenzo[c][1,2,5]thiadiazole as arms (S(TPA-BBT)) was synthesized and investigated as an electron acceptor in solution-processed organic solar cells. The compound S(TPA-BBT) shows excellent thermal stability with a decomposition temperature of 353 °C. S(TPA-BBT) in chloroform solution exhibits two absorption peaks at 326 and 450 nm, which red shifts to 334 and 482 nm in thin film, respectively. The HOMO and LUMO energies are estimated to be −5.48 and −3.10 eV, respectively, from electrochemistry, and match with those of poly(3-hexylthiophene) (P3HT). Solution-processed solar cells based on P3HT:S(TPA-BBT) after annealing at 150 °C for 10 min yield power conversion efficiencies up to 0.81%.