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We report the molecular engineering of new small molecule-based medium band gap nonfullerene acceptors containing a strong electron acceptor backbone of DPP attached to the $\pi$-spacer-based furan linker. We systematically designed five new designed molecules (H1−H5) and studied their structural, optical, photovoltaic and optoelectronic characteristics. We employed advanced quantum chemical approaches to characterize these molecules (H1–H5) and synthetic reference molecule R. The designed molecules exhibit improved light absorption and narrower energy bandgaps in contrast to R. Moreover, a lower excitation energy of these molecules (H1−H5) enables easier excitation and phase separation in the excited states. Analysis of the geometric and physiochemical properties provides evidence of the enhanced photovoltaic and optoelectronic characteristics of these molecules in comparison to the R molecule and other molecules with similar structures that have been previously reported. Among all these designed series, H3 stands out with a minimal 1.99 eV band gap, excellent hole (${\lambda }_h$ 0.0079 eV) and electron (${\lambda }_e$ 0.0076 eV) mobility, low binding energy ($E_b$ 0.42 eV) and highly red-shifted absorption characteristics. Furthermore, these molecules also displayed good electron and hole mobilities, indicating their tremendous potential in producing high-efficiency organic solar cells. Therefore, this study showcases the molecular modeling and effectiveness of these DPP and furan-containing molecules and their promising potential for organic photovoltaics.

Organic solar cells (OSCs) have attracted significant interest from researchers due to their low cost, high-power conversion efficiency (PCE), and ability to compensate for light deficits. Four new acceptor molecules (CC1–CC4) have been designed. Several parameters have been studied including frontier molecular orbital (FMO), density of states (DOS), transition density matrix (TDM), reorganizational energies of electrons and holes, open circuit voltage ($V_{\text{o}\text{c}})$, and charge transfer analysis. The designed molecules (CC1–CC4) show promising optoelectronic features, with a narrower energy gap (0.320–1.922 eV) and absorption properties demonstrating that designed molecules exhibit ${\lambda }_{\text{m}\text{a}\text{x}}$ (560–698 nm). Excitation energy values range from 1.776 eV to 2.216 eV, which is lower for all of the developed compounds. This study will help researchers to design molecules for the development of efficient OSCs.

We present a review of the recent progresses in solution processing graphene thin films and highlight some of the uses of graphene and graphene thin films in the construction of organic solar cells. We demonstrate a simple phenomenological model to describe the relationship between sheet conductivity and transmittance in graphene films with good agreement to all of the data found in the literature. We show that graphene thin films have been proven useful in the construction and improvement of organic solar cells not only as a replacement electrode, but also as an active acceptor material, or as a counter electrode when integrated into a conducting polymer matrix.

As a suitable recombination process, recombination via tail state in organic bulk-heterojunction solar cells (OBHJs) is capable of reproducing both dark and illuminated current–voltage curves. The characteristic parameters of OBHJs based on recombination via tail are governed by transportation and extraction efficiency, and both processes are strongly dependent on the charge carrier mobility. Using a macroscopic simulation, we calculate the mobility dependent power conversion efficiency, open-circuit voltage, short-circuit current and fill factor. The open-circuit voltage is determined by not only carrier density n(p), but also by carrier density gradient. Furthermore, open-circuit voltage is more affected by majority charge carriers and less affected by minority ones.

The mastery of the optoelectronic properties of conjugated copolymers by substituting their radicals is a promising way for increasing the light absorption and charge career transport in the organic devices active layer. In this paper, we present the chemical synthesis of four different conjugated benzaldehyde derivatives and pyrrole-based copolymers (P–P:B) followed by their conception in thin films on glass substrates by dip coating root from a solution in dichloromethane. UV–Vis measurements showed absorption in good part of the visible region, with an optical gap around 2 eV. Morphological properties observed by scanning electron microscope of the four P–P:B based thin films illustrated homogenous and continuous surfaces with roughness and surface shape that can be modulated according to Nitrobenzylidene derivative that contains the copolymer. First oxidation ($E_p$) and reduction ($E_n$) potentials of synthetized copolymers have been estimated by cyclic voltammetry which led us to estimate the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), respectively. The HOMO and LUMO energy level diagram of P–P:B compared with the most commonly used organic materials as donor/acceptor couples showed a cascade shape, which allowed us to opt for organic solar cells based on multiple active layers in our aim to improve its performance.

In this paper, AC and DC electrical properties of organic solar cells based on P3HT:PCBM active layer have been investigated. The performance of such solar cell has demonstrated the efficiency of 2.31% corresponding with short-circuit current density of 6.08 mA ⋅ cm${}^{-2}$, open circuit voltage of 0.64 V and fill factor of 60%. The equivalent circuit and the properties of the supposed interfaces between the layers in the P3HT:PCBM-based solar cell have been estimated. AC properties have demonstrated series capacitance increasing with increasing frequencies, which means series capacitance saves charges and parallel capacitance has decreased with increasing of frequency work as discharge part of charges stored in series capacitance. Also, equivalent series and parallel resistances have demonstrated a decrease from 7 $\mathrm{\Omega }$ and 120 k$\mathrm{\Omega }$ at low frequency to 1 $\mathrm{\Omega }$ and 43 k$\mathrm{\Omega }$ at high frequencies, respectively.

Organic solar cells have become a center of attention in the field of research and technology due to its remarkable features. In the current research work, we designed Benzo Thiophene (BT-CIC) based non-fullerene acceptor organic solar cell having A-D-A novel structure. The designed structures D1-D4 were derived from BT-CIC (non-fullerene acceptor) by replacing 2-(5,6-dichloro-2-methylene-3-oxo-2,3-dihydro-1H-inden-1-ylidene)acetonitrile of reference molecule R with different electron withdrawing end-capper acceptor moieties. The effect of end acceptor groups on absorption, energy level, charge transport, morphology, and photovoltaic properties of the designed molecules (D1-D4) were investigated by TD-DFT B3LYP/6-31G basic level of theory and compared with reference molecule R. Among all novel structures, D3 exhibited maximum absorption (${\lambda }_{max}$) of 701.7nm and 755.2nm in gaseous state anfd chloroform, respectively. The red shift in D3 was due to the presence of strong electron withdrawing acceptor moiety and more extended conjugation as compared to other structures. D3 also displayed lowest values of energy bandgap (1.97 eV), ${\lambda }_e$ (0.0063eV) and ${\lambda }_h$ (0.0099eV) and which signify its ease electron mobility. Lowest value of binding energy 1.20eV of D3 suggested that this molecule could be easily dissociated into charge carriers TDM results revealed that easy exciton dissociation occurred in D3. Overall, designed structure D3 was found to be more effective and efficient acceptor molecule for SMOSCs. The findings provide novel information for the development of non-fullerene acceptors for OPVs.

Herein, we have designed four small molecular donors (SMDs) with Donor–Acceptor–Acceptor (D–Á–A) backbone having different acceptor units for highly efficient organic solar cells (OSCs). The specific molecular modeling has been made by replacing the additional acceptor unit (A) of recently synthesized TPA-DAA-MDN molecule (R) by employing different highly efficient acceptor units in order to improve the photovoltaic performances of the molecules. A theoretical approach (DFT and TD-DFT) has been applied to investigate the photophysical, opto-electronic and photovoltaic parameters of the designed molecules (DAA1–DAA4) and compared with the reference molecule (R). The red-shifting absorption of SMDs is the most important factor for highly efficient OSCs. Our all formulated molecules showed a red shifted absorption spectrum and also exhibit near IR sensitivity. Acceptor unit modification of R molecule causes reduction in HOMO-LUMO energy gap; therefore, all designed molecules offer better opto-electronic properties as compared to R molecule. A variety of certain critical factors essential for efficient SMDs like frontier molecular orbitals (FMOs), absorption maxima, dipole moment, exciton binding energy along with transition density matrix, excitation energy, open circuit voltages and charge mobilities of (DAA1–DAA4) and R have also been investigated. Generally, low values of reorganizational energy (hole and electron) offer high charge mobility and our all designed molecules are enriched in this aspect. High open circuit voltage values, low excitation energies, large dipole moment values indicate that our designed SMDs are suitable candidates for high-efficiency OSCs. Furthermore, conceptualized molecules are superior and thus are suggested to experimentalist for out-looking future progresses of highly efficient OSCs devices.

Phthalocyanines, porphyrins and analogs are highly versatile and stable molecules with an extended π-aromatic system and high extinction coefficients, making them suitable for integration in solar cells as photoactive components and/or as light-harvesting materials. The most significant results by Spanish groups in the field are collected in this report.

We designed and synthesized anthryl-disubstituted magnesium tetraethynylporphyrin([{5,15-bis(anthracen-9′-yl)ethynyl}-10,20-bis{(triisopropylsilyl)ethynyl}porphyrinato] magnesium(II)), and applied it as an electron donor to solution-processed bulk heterojunction small molecule organic solar cells. The compound was characterized by single crystal X-ray crystallography as well as UV-vis light absorption spectrum showing the absorption maximum and onset at 700 and 740 nm, respectively. Organic solar cells using this compound and [6,6]-phenyl-C61-butyric acid methyl ester (PC₆₁BM) as electron donor and acceptor, respectively, showed power conversion efficiency of 1.31% at the donor and acceptor ratio of 1:3. The use of pyridine as a coordinating additive increased power conversion efficiency to 1.61%, which was the best among tested additives, THF, pyradine, dioxane, and 1,8-diiodooctane.

We synthesized a diporphyrin compound [4,7-bis[5-[arylethynyl]-10,20-bis{(triisopropylsilyl)ethynyl}porphyrin-15-yl]]-2,1,3-benzothiadiazole dimagnesium(II)], in which two porphyrin units were linked using a benzodiathiazole unit as an electron-withdrawing moiety. These diporphyrins have low-lying HOMO and LUMO levels with long-wavelength light absorption property. Power conversion efficiency of the organic solar cell using this diporphyrin and mix-PCBM (a 85:15 mixture of [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) was 2.75% with short-circuit current density of 8.79 mA/cm², open-circuit voltage of 0.80 V, and fill factor of 0.39. Photocurrent conversion in the near infrared region was demonstrated by the incident photon-to-current efficiency spectrum.

The copper(II), nickel(II), etc. complexes of 5,15-bis(trimethylsilylethynyl)tetrabenzoporphyrin (TMS-H₂BP) and 5,15-bis(triisopropylsilylethynyl)tetrabenzoporphyrin (TIPS-H₂BP) have been prepared from the corresponding bicycle[2.2.2]octadiene(BCOD)-fused precursors by the retro-Diels–Alder reaction. X-ray diffraction (XRD) analyses show that TMS-H₂BP and its metal complexes of zinc(II) (TMS-ZnBP) and copper(II) (TMS-CuBP) adopt flat molecular conformations and form herringbone-type packing structures in the single crystalline state. TIPS-H₂BP and the zinc(II) and copper(II) complexes (TIPS-ZnBP and TIPS-CuBP) are similar to the TMS derivatives in molecular conformation, but these TIPS derivatives form one-dimensional slipped-stack structures. The nickel complexes TMS-NiBP and TIPS-NiBP have U-shaped structures because of the small size of nickel(II) ion. Solution processed organic thin-film transistors of the benzoporphyrins were fabricated and TMS-H₂BP showed the highest hole mobility of 0.11 cm².V^-1.s^-1. Bulk heterojunction organic solar cells based on TMS- or TIPS-H₂BP and their metal complexes as p-type and PC₇₁BM as n-type materials were fabricated by solution process. Atomic force microscopy and thin-film XRD measurements indicated that the film crystallinities were increased by raising the annealing temperature over 180°C or by changing the substituents from triisopropylsilyl to trimethylsilyl. The best power-conversion efficiency (PCE) of 1.49% was achieved with TMS-ZnBP by annealing at 180°C with a moderate crystallinity and smooth surface.

A series of symmetrically substituted subphthalocyanine derivatives with diverse substituent such as electron-donating or electron-withdrawing moieties at the peripheral position have been synthesized and their photophysical and electrochemical properties have been investigated. Solution-processed bulk heterojunction (BHJ) organic solar cells using SubPc derivatives as electron donor and fullerene derivative PCBM as an electron acceptor in the active layer were fabricated and characterized to evaluate the photovoltaic behavior of these molecules.

A novel asymmetrical zinc(II) phthalocyanine-BODIPY conjugate (ZnPc-BODIPY) bearing three iodine groups directly substituted to the macrocycle and one BODIPY connected to the macrocycle with an amide bond was synthesized by the reaction of carboxylic-acid-substituted asymmetrical zinc(II) phthalocyanine (ZnPc) with the BODIPY-derivative-bearing amino group (BODIPY-NH₂). This conjugate was fully characterized by spectroscopic methods (FT-IR, UV-vis, ¹H NMR, ¹¹B NMR, ¹⁹F NMR and mass) and elemental analysis. The fluorescence behavior of ZnPc-BODIPY was studied to determine the energy transfer process. Voltammetry measurements (CV and SWV) were performed to specify the HOMO–LUMO energy levels and band gaps of ZnPc-BODIPY and starting compounds (ZnPc and BODIPY-NH₂) for comparison. In addition, the band gaps of these compounds were also determined by UV-vis absorption onset (λ_onset) and theoretical calculations. Bulk heterojunction solar cells containing ZnPc-BODIPY were fabricated in the structure of ITO/PEDOT:PSS/ZnPc-BODIPY:PCBM/Al. The photovoltaic parameters of the solar cell were obtained and the ZnPc-BODIPY conjugate was found to bring spectral contribution to IPCE at a peak of 510 nm.

A new zinc phthalocyanine–benzoquinone rigid dyad, QnZnPc–G${}_2$ was synthesized as a model compound to study photo-induced charge separation mimicking natural photosynthesis. Compared to its previously reported analog, this dyad has an additional fused benzene ring between the zinc phthalocyanine (ZnPc) (donor) and benzoquinone (acceptor) moieties. The rigid structure of QnZnPc–G${}_2$ ($i.e.$ no rotamers) is designed to minimize the unusual electronic perturbation induced by the internal motions, which resulted in a significant increase in the lifetime of the charged separated state (from 40 ps to 252 ps). Physical and photochemical properties of this new dyad were examined and discussed in this paper.

Magnesium diethynylporphyrin derivatives with strong near-infrared absorption were obtained. These derivatives possess electron rich units directly introduced to the porphyrin core. The electron rich units caused strong absorption on the near-infrared region due to an intramolecular charge transfer. Theoretical calculation also proved that the derivatives showed large oscillator strength at the Q band. As a donor material, such large absorption coefficient in the range of long wavelength region is a desirable characteristic for organic solar cells. Organic photovoltaic devices using these diethynylporphyrin derivatives gave a PCE of 2.91% in optimal conditions.

Imide-based Subphthalocyanines (SubPcs) is gaining momentum as non-fullerene acceptors in organic solar cells (OSCs). Herein we report the synthesis, characterization, and photovoltaic performance of Perylenemonoimide (PMI)-SubPc conjugates in which the PMI is linked to the SubPc core by either alkynes or direct C-C bond. These derivatives are prepared via palladium-catalyzed cross-coupling reactions. The introduction of PMI units results in a red-shifted absorption, which can be described as the combination of the absorption properties of both SubPc and PMIs fragments. The absorption spectra are thus mainly composed of two transitions, one derived from the SubPc Q-band and the other from transitions within the PMI moieties. These PMI-SubPc systems exhibit moderate acceptor properties and therefore their use as non-fullerene acceptors in bulk-heterojunction organic solar cells is briefly explored.

A new molecule with dithieno[3,2-b:2’,3’-d]pyrrole (DTP) as central moiety and two terminal diketopyrrolopyrrole (DPP) units named DPP-DTPC8 has been designed and synthesized. The push–pull molecule exhibits excellent thermal stability, strong absorption in visible region, and matched energy levels. Devices fabricated from DTPC8:PC${}_{71}$BM blend films exhibit the maximum power conversion efficiency of 2.75%, with Voc of 0.63 V, Jsc of 9.94 mA$\cdot$ cm${}^{-2}$, and FF of 43.8%. The active layers undergo thermal annealing or solvent vapor annealing treatments, exhibiting inconspicuous influence on the aggregation of the molecule. This study demonstrates that the new molecule DPP-DTPC8 tailored with DTP and DPP units could affect the thermal stability, absorption, energy levels and morphology that manage the photovoltaic performances.

A novel non-fullerene small molecule acceptor named DPPMDPC6 with diketopyrrolopyrrole (DPP) as central moiety and methyl-dioxocyano-pyridine (MDP) units as two branches has been designed and synthesized. Benefitted from the quinoidal MDP segment, the molecule exhibits effective electron delocalization extending to the near infrared (NIR) region absorption with narrow bandgap of 1.42eV. The acceptor also displayed intrinsic properties with good thermal stability, and matched energy levels with various donor materials especially for the commercial polymer PTB7. Under optimized condition, the devices fabricated by forming PTB7:DPPMDPC6 blend films yield a moderate PCE of 5.80% with a $V_{\mathrm{\text{oc}}}$ of 0.84V, a $J_{\mathrm{\text{sc}}}$ of 12.94mA$\cdot$cm${}^{-2}$, and an FF of 53.4%. This preliminary study demonstrates that the new acceptor tailored with quinoidal MDP units could lead to enhancement on the low energy absorption band that is favorable for the photovoltaic performances.

Nonfullerene electron acceptor materials have gained enormous attention due to their potential as replacements of fullerene electron acceptors in bulk heterojunction organic solar cells. A novel thiophene bridged selenophene-containing perylene diimide acceptor PDISe-T has been synthesized and applied as an acceptor in nonfullerene organic photovoltaic cells. The inverted organic photovoltaic (OPV) solar cells based on PDISe-T:PBT7-Th (acceptor:donor) blends give a power conversion efficiency (PCE) value of 2.53% with an open-circuit voltage ($V_{\mathrm{\text{oc}}})$ of 0.92V, a $J_{\mathrm{\text{sc}}}$ of 6.55mAcm${}^{-2}$, and a fill factor (FF) of 0.42.