Organic Solar Cells Based on Non-Fullerene Low Molecular Weight Organic Semiconductor Molecules.

The development of narrow bandgap A-D-A- and ADA'DA-type non-fullerene small molecule acceptors (NFSMAs) along with small molecule donors (SMDs) have led to significant progress in all-small molecule organic solar cells. Remarkable power conversion efficiencies, nearing the range of 17-18 %, have been realized. These efficiency values are on par with those achieved in OSCs based on polymeric donors.

Dibenzoquinone Cyclopentadithiophene Diradicaloids Show Optical Transitions of Different Spin States and Anomalous Near-Infrared Emission.

We have prepared a series of bis(semiquinone) compounds with dithiophene bridges of different length that evolve from closed-shell (smaller compound) to full diradical (longer compound) for which the narrow singlet-triplet energy gap allows the triplet population at 298 K. The medium size system has a variety of photonic properties with absorptions and emission in the optical near-infrared region mediated by a unique case of anti-Kasha emission. A whole set of optical absorption/emission and vibrational steady state spectroscopies as well as picosecond transient absorption spectroscopy, all complemented with spectroelectrochemistry and theoretical calculations, is presented.

Effects of Halogenation on Cyclopentadithiophenevinylene-Based Acceptors with Excellent Responses in Binary Organic Solar Cells.

In recent years, non-fused non-fullerene acceptors (NFAs) have attracted increasing consideration due to several advantages, which include simple preparation, superior yield, and low cost. In the work reported here, we designed and synthesized three new NFAs with the same cyclopentadithiophenevinylene (CPDTV) trimer as the electron-donating unit and different terminal units (IC for , IC-4F for , and IC-4Cl for ). Both halogenated NFAs, i.

Gold(III) Porphyrin Was Used as an Electron Acceptor for Efficient Organic Solar Cells.

The widespread use of nonfullerene-based electron-accepting materials has triggered a rapid increase in the performance of organic photovoltaic devices. However, the number of efficient acceptor compounds available is rather limited, which hinders the discovery of new, high-performing donor:acceptor combinations. Here, we present a new, efficient electron-accepting compound based on a hitherto unexplored family of well-known molecules: gold porphyrins.

Self-Assembly-Directed Organization of a Fullerene-Bisporphyrin into Supramolecular Giant Donut Structures for Excited-State Charge Stabilization.

Functional materials composed of spontaneously self-assembled electron donor and acceptor entities capable of generating long-lived charge-separated states upon photoillumination are in great demand as they are key in building the next generation of light energy harvesting devices. However, creating such well-defined architectures is challenging due to the intricate molecular design, multistep synthesis, and issues associated in demonstrating long-lived electron transfer. In this study, we have accomplished these tasks and report the synthesis of a new fullerene-bis-Zn-porphyrin -bisadduct by tether-directed functionalization of C via a multistep synthetic protocol.

Fullerene/Non-fullerene Alloy for High-Performance All-Small-Molecule Organic Solar Cells.

Organic solar cells (OSCs) that contain small molecules only were prepared with as the donor, a narrow band gap non-fullerene acceptor , and a wide band gap PCBM. The OSCs based on optimized : (1:1.2) and :PCBM (1:1.

Reducing Energy Loss in Organic Solar Cells by Changing the Central Metal in Metalloporphyrins.

The effect of central donor core on the properties of A-π-D-π-A donors, where D is a porphyrin macrocycle, cyclopenta[2,1-b:3,4-b']dithiophene is the π bridge, and A is a dicyanorhodanine terminal unit, was investigated for the fabrication of the organic solar cells (OSCs), along [6,6]-phenyl-C71-butyric acid methyl ester (PC BM) as electron acceptor. A new molecule consisting of Ni-porphyrin central donor core (VC9) showed deep HOMO energy level and OSCs based on optimized VC9:PC BM realized overall power conversion efficiency (PCE) of 10.66 % [short-circuit current density (J )=15.

Synthesis and electronic properties of pyridine end-capped cyclopentadithiophene-vinylene oligomers.

A series of four oligomers of cyclopentadithiophene-vinylenes end capped with pyridine groups was prepared and their optical and electronic properties studied. Treatment with trifluoroacetic acid (TFA) leads to the bisprotonation of the nitrogens of the pyridine, which has an important impact on the optical properties. Excess treatment with TFA provokes the oxidation of the conjugated core, generating radical cations and dications.

Near-IR Absorbing D-A-D Zn-Porphyrin-Based Small-Molecule Donors for Organic Solar Cells with Low-Voltage Loss.

Two D-A-D small molecules with a DPP acceptor core and Zn-porphyrin donor with different electron-donating substituents, namely, 2,6-bis(dodecyloxy)phenyl and 5-hexylthieno[3,2- b]thiophen-2-yl at mesopositions, VC4 and VC5, were synthesized, and their optical and electrochemical properties were investigated. The results reveal that both molecules are suitable as donors for organic solar cells (OSCs) in which PCBM is employed as the acceptor. Overall power conversion efficiencies of 8.

Ni-Porphyrin-based small molecule for efficient organic solar cells (>9.0%) with a high open circuit voltage of over 1.0 V and low energy loss.

A new A-π-D-π-A small molecule with a Ni-porphyrin core (MV143) has been synthesized and employed as a donor, along with PC71BM, for the fabrication of solution-processed bulk heterojunction OSCs organic solar cells. The device exhibited an overall PCE of 9.14% (JSC = 13.

Panchromatic ternary organic solar cells with 9.44% efficiency incorporating porphyrin-based donors.

In an effort to improve the short-circuit current and fill factor, organic solar cells have been developed with ternary blending in a single bulk heterojunction active layer. We report here several all small molecule organic solar cells based on ternary bulk heterojunction active layers. These layers consist of two small molecule porphyrin donors (MV71 and MV72), which have the same backbone but different end-capping acceptor units, and PC71BM as the acceptor.

Oligomers of cyclopentadithiophene-vinylene in aromatic and quinoidal versions and redox species with intermediate forms.

A new series of π-conjugated oligomers based on the 4,4 dihexyl-4-cyclopenta[2,1-:3,4-']dithiophene vinylene repeating unit has been prepared and characterized by X-ray, electrochemical, spectroscopic (UV-Vis absorption, emission and Raman) and density functional theory methods. The oligomers in their neutral, oxidized and reduced forms have been investigated. The neutral compounds show a longer mean conjugation length than oligothiophenes and oligothiophene-vinylenes and display very rich redox chemistry with the stabilization of polycationic states of which the radical cations and dications are strong NIR absorbers, the latter displaying singlet diradicaloid character.

Pyrrolo[3,2-b]pyrrole as the Central Core of the Electron Donor for Solution-Processed Organic Solar Cells.

A series of three small-molecule acceptor-donor-acceptor (A-D-A) compounds with a tetraaryl-1,4-dihydropyrrolo[3,2-b]pyrrole as the central building block were synthesized and fully characterized. These molecules present high thermal stability and suitable HOMO-LUMO energy levels making them feasible electron-donor materials in bulk heterojunction organic solar cells (BHJ-OSC). Moreover, theoretical work predicts of a lack of planarity and no π-π stacking, furthermore.

Efficient Polymer Solar Cells with High Open-Circuit Voltage Containing Diketopyrrolopyrrole-Based Non-Fullerene Acceptor Core End-Capped with Rhodanine Units.

Herein we report the synthesis of a novel A-D-A-D-A non-fullerene small-molecule acceptor (NFSMA) bearing a diketopyrrolopyrrole (DPP) acceptor central core coupled to terminal rhodanine acceptors via a thiophene donor linker (denoted as MPU1) for use in non-fullerene polymer solar cells (PSCs). This NFSMA exhibits a narrow optical band gap (1.48 eV), strong absorption in the 600-800 nm wavelength region of the solar spectrum, and a lowest unoccupied energy level of -3.

Cyclopentadithiophene organic core in small molecule organic solar cells: morphological control of carrier recombination.

Two new planar and symmetrical A-D-A (electron acceptor-electron donor-electron acceptor) small molecules based on a commercial cyclopentadithiophene derivative have been synthesized for solution processed small molecule organic solar cells. The aim was to synthesise the molecules to be energetically identical (similar HOMO-LUMO energy levels) in order to assign the differences observed to changes in the film morphology or to differences in the interfacial recombination kinetics or both. Devices were electrically characterized under one sun simulated (1.

Regioselective preparation of a bis-pyrazolinofullerene by a macrocyclization reaction.

A single isomer of a pyrazolinofullerene bis-adduct was prepared by tether-directed remote functionalization. Specifically, a macrocyclization reaction between C and a bis-hydrazone reagent has been carried out to generate a regioisomerically pure fullerene bis-adduct which presents a lower LUMO than pristine C.

Efficiency improvement using bis(trifluoromethane) sulfonamide lithium salt as a chemical additive in porphyrin based organic solar cells.

Two new conjugated acceptor-π-donor-π-acceptor (A-π-D-π-A) porphyrins have been synthesised using 3-ethylrhodanine (1a) or dicyanovinylene (1b) groups as acceptor units. Their optical and electrochemical properties made these materials excellent electron donors along with PCBM as the acceptor for solution-processed bulk heterojunction organic solar cells. The devices based on 1a:PCBM (1 : 2) and 1b:PCBM (1 : 2) processed with CB showed low power conversion efficiencies (PCE) of 2.

Role of the bridge in photoinduced electron transfer in porphyrin-fullerene dyads.

The role of π-conjugated molecular bridges in through-space and through-bond electron transfer is studied by comparing two porphyrin-fullerene donor-acceptor (D-A) dyads. One dyad, ZnP-Ph-C60 (ZnP = zinc porphyrin), incorporates a phenyl bridge between D and A and behaves very similarly to analogous dyads studied previously. The second dyad, ZnP-EDOTV-C60, introduces an additional 3,4-ethylenedioxythienylvinylene (EDOTV) unit into the conjugated bridge, which increases the distance between D and A, but, at the same time, provides increased electronic communication between them.

Robust ethylenedioxythiophene-vinylene oligomers from fragile thiophene-vinylene cores: synthesis and optical, chemical and electrochemical properties of multicharged shapes.

Oligomers of ethylendioxythiophene-vinylene have been prepared. Their optical, electrochemical and chemical properties have been studied in detail by absorption and emission spectroscopy as well as cyclic voltammetry, Raman techniques and spectroelectrochemistry complemented with quantum chemical calculations. A comparison with their non-ethylendioxy and non-vinylene parents has been done.

Photoinduced electron transfer of zinc porphyrin-oligo(thienylenevinylene)-fullerene[60] triads; thienylenevinylenes as efficient molecular wires.

Two novel donor-bridge-acceptor arrays (ZnP-nTV-C60) with zinc porphyrin (ZnP) and fullerene (C60), covalently connected by oligo(thienylenevinylene) (nTV) molecular wires (n = 3 and 8; ), have been prepared in a multistep convergent manner. The influence of the nTV-length on the electrochemical and electronic properties of the ZnP-nTV-C60 triads has been revealed. Interestingly, an efficient photoinduced electron transfer process occurs in both triads with formation of intermediate radical-ion pairs (namely, ZnP˙(+)-nTV-C60˙(-) and ZnP-nTV˙(+)-C60˙(-)) as confirmed by the nanosecond transient absorption measurements in the visible and NIR regions.

Organic dyes incorporating oligothienylenevinylene for efficient dye-sensitized solar cells.

Two new organic dyes incorporating triphenylamine as a donor and oligothienylenevinylene as a bridge have been synthesized. The new dyes cover the entire visible region and have a power conversion of up to 6.25%.

Delocalization-to-localization charge transition in diferrocenyl-oligothienylene-vinylene molecular wires as a function of the size by Raman spectroscopy.

In going from short to large size thienylene-vinylene diferrocenyl cations, the transition from a charge delocalized to a localized state is addressed by resonance Raman spectroscopy and supported by theoretical model chemistry. The shorter members, dimer and tetramer, display conjugated structures near the cyanine limit of bond length equalization as a result of the strong interferrocene charge resonance, producing a full charge delocalized mixed valence system. In the longest octamer, charge resonance vanishes and the cation is localized at the bridge center (the mixed valence property disappears).

Panchromatic push-pull chromophores based on triphenylamine as donors for molecular solar cells.

Two new push-pull chromophores based on triphenylamine as donor and 2-carboxymethyl-2-cyanomethylenethiazole as acceptor have been synthesized. Both exhibit strong light absorption covering from 300 to 800 nm. Electrochemical studies show HOMO-LUMO gaps of 2.

Synthesis and photoinduced energy- and electron-transfer processes of C60-oligothienylenevinylene-C70 dumbbell compounds.

Unsymmetric dumbbell molecules based on N-methylpyrrolidine[60]fullerene, oligothienylenevinylenes (nTV; n=2, 4), and N-methylpyrrolidine[70]fullerene, namely, C(60) -nTV-C(70) were synthesized and their photophysical properties were studied. In nonpolar solvents, photoinduced energy-transfer process predominantly takes place from the singlet excited state of nTV to C(60) and C(70) , as was confirmed by time-resolved emission and transient absorption spectroscopy. In polar solvent, charge-separation processes take place instead of energy transfer.