The Cover Feature shows new non‐fullerene acceptor molecules that could help meet industrial needs and facilitate the manufacture of organic solar cells. More information can be found in the Full ...Paper by Y. A. Avalos‐Quiroz et al.
Dicarboxyterpyridine chelates with π-conjugated pendant groups attached at the 5- or 6-position of the terminal pyridyl unit were synthesized. Together with 2,6-bis(5-pyrazolyl)pyridine, these were ...used successfully to prepare a series of novel heteroleptic, bis-tridentate Ru(II) sensitizers, denoted as TF-11–14. These dyes show excellent performance in dye-sensitized solar cells (DSCs) under AM1.5G simulated sunlight at a light intensity of 100 mW cm–2 in comparison with a reference device containing Ru(Htctpy)(NCS)3TBA3 (N749), where H3tctpy and TBA are 4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine and tetra-n-butylammonium cation, respectively. In particular, the sensitizer TF-12 gave a short-circuit photocurrent of 19.0 mA cm–2, an open-circuit voltage (V OC) of 0.71 V, and a fill factor of 0.68, affording an overall conversion efficiency of 9.21%. The increased conjugation conferred to the TF dyes by the addition of the π-conjugated pendant groups increases both their light-harvesting and photovoltaic energy conversion capability in comparison with N749. Detailed recombination processes in these devices were probed by various spectroscopic and dynamics measurements, and a clear correlation between the device V OC and the cell electron lifetime was established. In agreement with several other recent studies, the results demonstrate that high efficiencies can also be achieved with Ru(II) sensitizers that do not contain thiocyanate ancillaries. This bis-tridentate, dual-carboxy anchor configuration thus serves as a prototype for future omnibearing design of highly efficient Ru(II) sensitizers suited for use in DSCs.
In this article, we have designed and synthesized a porphyrin with the following molecular architecture A–π–D–π–A in which ethyl rhodanine end capping groups were linked to the core porphyrin donor ...via an octyl thiophene-ethynylene π bridge denoted as VC117 and used it as an electron donor along with (6,6-phenyl C 71 butyric acid methyl ester) (PC 71 BM) as an electron acceptor for the fabrication of solution processed organic solar cells. The solution processed BHJ organic solar cell with an optimized weight ratio of 1 : 1 VC117 : PC 71 BM in THF (tetrahydrofuran) showed an overall power conversion efficiency (PCE) of 2.95% with short circuit current J sc = 8.34 mA cm −2 , open circuit voltage V oc = 0.82 V and fill factor FF = 0.43. Nonetheless, when the active layer of the solar cell was processed from a mixture of 4% v/v of pyridine in THF solvent, it achieved a PCE value of 4.46% and further improved up to 5.50% after thermal annealing. This is ascribed to the enhancement of both the J sc and FF values. The higher value of J sc is explained by the increased absorption profile of the blend, the higher incident photon to current efficiency (IPCE) response and the better crystallinity of the active layer when processed with solvent additives and thermal annealing while the enhancement of FF is due to the better charge transport capability and the charge collection efficiency of the latter device.
The synthesis of four non‐fullerene acceptors (NFAs) with a “A–π–D–π–A” structure, in which the electron‐donating core is extended, was achieved. The molecules differed by the nature of the ...solubilizing groups on the π‐spacer and/or the presence of fluorine atoms on the peripheral electron‐accepting units. The optoelectronic properties of the molecules were characterized in solution, in thin film, and in photovoltaic devices. The nature of the solubilizing groups had a minor influence on the optoelectronic properties but affected the organization in the solid state. On the other hand, the fluorine atoms influenced the optoelectronics properties and increased the photo‐stability of the molecules in thin films. Compared to reference ITIC, the extended molecules showed a wider absorption across the visible range and higher lowest unoccupied molecular orbital energy levels. The photovoltaic performances of the four NFAs were assessed in binary blends using PM6 (PBDB‐T‐2F) as the donating polymer and in ternary blends with ITIC‐4F. Solar cells (active area 0.27 cm2) showed power conversion efficiencies of up to 11.1 % when ternary blends were processed from non‐halogenated solvents, without any thermal post‐treatment or use of halogenated additives, making this process compatible with industrial requirements.
The third component: Four non‐fullerene acceptors (NFAs) with an extended π‐conjugated core are synthesized and their optoelectronic properties are fully described. The fluorinated NFAs are soluble in non‐halogenated solvents and demonstrate a high photochemical stability. It is shown that they can be advantageously used as third components in ternary blends with PM6 and ITIC‐4F for the fabrication of high‐efficiency, post‐treatment‐free organic solar cells.
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•Two D1-A-D2-A-D1 small molecules (SMs) denoted as VC97 and VC97 were synthesized.•SMs consist different central donor unit and same BT as π-acceptor and end capping TPA.•These small ...molecules were used as donor for the fabrication of BHJ solar cells.•The optimized VC96:PC71BM (TASA processed) based device showed PCE of 6.13%.
Two molecules denoted as VC96 and VC97 have been synthesized for efficient (η=6.13% @ 100mW/cm2 sun-simulated light) small molecule solution processed organic solar cells. These molecules have been designed with the D1-A-D2-A-D1 structure bearing different central donor unit, same benzothiadiazole (BT) as π-acceptor and end capping triphenylamine. Moreover, the optical and electrochemical properties (both experimental and theoretical) of these molecules have been systematically investigated. The solar cells prepared from VC96:PC71BM and VC97:PC71BM (1:2) processed from CF (chloroform) exhibit a PCE (power conversion efficiency) of η=4.06% (Jsc=8.36mA/cm2, Voc=0.90V and FF=0.54) and η=3.12% (Jsc=6.78mA/cm2, Voc=0.92V and FF=0.50), respectively. The higher PCE of the device with VC96 as compared to VC97 is demonstrated to be due to the higher hole mobility and broader IPCE spectra. The devices based on VC96:PC71BM and VC97:PC71BM processed with solvent additive (3 v% DIO, 1,8-diiodooctane) showed PCE of η=5.44% and η=4.72%, respectively. The PCE device of optimized VC96:PC71BM processed with DIO/CF (thermal annealed) has been improved up to 6.13% (Jsc=10.72mA/cm2, Voc=0.88V and FF=0.61). The device optimization results from the improvement of the balanced charge transport and better nanoscale morphology induced by the solvent additive plus the thermal annealing.
Recently in Joule, Peng Wang et al. reported the fabrication of efficient and stable dye-sensitized solar cells (DSSCs) by employing two organic dyes with ionic-liquid-based electrolyte. For the ...first time, they demonstrated a power conversion efficiency of 10% in association with high stability, assessed through accelerated aging tests.
Recently in Joule, Peng Wang et al. reported the fabrication of efficient and stable dye-sensitized solar cells (DSSCs) by employing two organic dyes with ionic-liquid-based electrolyte. For the first time, they demonstrated a power conversion efficiency of 10% in association with high stability, assessed through accelerated aging tests.
The synthesis, characterization, electrochemical and photophysical properties of a novel D- pi -A indoline organic dye, VCL01, are described. Its performance characteristics in dye sensitized solar ...cell (DSC) devices under standard AM 1.5G illumination are also investigated. VCL01 incorporates a cyclopentadithiophene unit as the pi -bridge between the indoline donor and cyanoacetic acceptor units. In comparison with the reference dye LS-1 containing only one thiophene unit in the pi -bridge, VCL01 shows a 40 nm red shift in adsorption, an increase in molar absorptivity and a 0.17 V lower oxidation potential, all consistent with the more conjugated nature of this sensitizer. The efficiencies of VCL01 and LS-1 DSC devices were 4.81% and 6.23%, respectively, which upon >100 min continuous light soaking under AM 1.5G illumination rose to 7.21% and 6.95%, representing an unprecedented 50% increase in efficiency for the VCL01 device. This increase is overwhelmingly due to an increase in photocurrent but, remarkably, V sub(oc) also increases by 50 mV upon illumination reflected in transient photovoltage data which indicate that electron lifetime increases considerably also. Time-correlated single photon counting data indicate that the light soaking effect can be partly attributed to improved TiO sub(2)/dye interaction leading to enhanced electron injection.
Three D-π-A-π-A organic dyes (QX1, DTQX1 and TPZ1) were synthesized and used as photosensitizers in Dye Sensitized Solar Cells (DSSC). The molecules only vary by the nature of the linker connecting a ...side dithienylpyrazine motive to a triarylamine-based donating unit and a phenylcyano-acrylic acid to provide the anchoring function. By simply swapping the aromatic connecting unit the range and intensity of the absorption of the compounds can be tuned, leading to orange and green dyes. The energy levels of the frontier orbitals are well-positioned for use in DSSC with TiO2 as the photoanode and I−/I3− as a redox couple in the electrolyte. Solar cells based on these sensitizers showed a power conversion efficiency (PCE) of up to 8.6% for the dyes with the narrower absorption. The lower PCE with TPZ1 is attributed to the more quinoidal nature of the π-conjugated backbone, which leads to a less favorable spatial distribution of the frontier orbitals and results in lower electron injection and higher recombination rate.
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•Novel small molecules using indoline as electron donor for efficient organic solar cells.•The differences in efficiency can be explained by the differences in light harvesting and ...charge recombination.•The pi-bridge results key to achieve high photocurrent and slow charge recombination kinetics.•No clear correlation between charge mobility, film morphology and solar cell efficiency.
In this work we have synthesized and characterized four indoline-based small organic molecules for their use as electron donor moiety in bulk-heterojunction solution processed organic solar cells combined with PC70BM as electron acceptor. Our results show a wide range of light to energy efficiencies from 0.8% to 3.5% under standard measurement conditions. An initial analysis suggests that the main limitation is the device photocurrent due to the device film thickness. Yet, charge transfer dynamics were studied to correlate charge loss mechanisms to π-bridge structural variations and, moreover, mobility measurements were also carried out to fully explain these device limitations.
In this work we report how crucial is the correct design of the porphyrin sensitizers in Dye Sensitized Solar Cells (DSSCs). Only a single atom change
switches-on
the efficiency from 2-3% to over 10% ...under standard measurement conditions. We used the 2,1,3-benzothiadazole (BDT) group, as a π-conjugated linker, for the porphyrin
LCVC01
, a thiophene moiety for the porphyrin
LCVC02
and also the furan group for the
LCVC03
porphyrin, as molecular spacers between the BDT fragment and the molecule anchoring group, respectively. These three porphyrins were investigated for their application in DSSC devices. All the devices were characterized and found to achieve a record cell efficiency of 10.5% for
LCVC02
but only 3.84% and 2.55% for
LCVC01
and
LCVC03
respectively. On one hand, the introduction of a thiophene, instead of a furan group, illustrates the importance of introducing a chemical group as a spacer, such as thiophene, between the BDT and the anchoring group. On the other hand, the selection of this group has to be correct because the change of a single atom increases the charge recombination rate and decreases the device performance. These changes can be rationalized by analyzing the dye dipoles and their interactions.
In this work we report how crucial is the correct design of the porphyrin sensitizers in Dye Sensitized Solar Cells (DSSCs).
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