Ring Electron Acceptors Research Articles

Simple High-Performance Nonfused Ring Electron Acceptors With Well-Controlled Terminal Group Stacking

Simple High-Performance Nonfused Ring Electron Acceptors With Well-Controlled Terminal Group Stacking

Dual-Functional Ambipolar Non-Fused Ring Electron Acceptor as Third Component and Designing Similar Molecular Structure between Two Acceptors for High-Performance Ternary Organic Solar Cells

Dual-Functional Ambipolar Non-Fused Ring Electron Acceptor as Third Component and Designing Similar Molecular Structure between Two Acceptors for High-Performance Ternary Organic Solar Cells

Near-infrared non-fused ring acceptors with light absorption up to 1000 nm for efficient and low-energy loss organic solar cells

It is challenging to afford both high-performance and low-energy loss (Eloss) organic solar cells (OSCs) based on near-infrared (NIR) non-fused ring electron acceptors (NFREAs) with ultra-narrow bandgap. Herein, three simple NFREAs (C6OT-4F, C6EDOT-4F and PDOT-4F) with absorption up to 1000 nm are developed by using alkoxy substituted thiophene derivatives core connected to fluorinated 1,1-dicyanomethylene-3-indanone (DFIC) terminals through 4H-cyclopenta[1,2-b:5,4-b’]dithiophene (CPDT) bridge. It is found that fine tuning central thiophene derivatives can surprisingly lead to different photoelectric properties and the device performances. Compared with C6EDOT-4F and PDOT-4F, C6OT-4F shows a blue-shifted absorption and an elevated LUMO level, which is beneficial for boosting Voc. As a result, optimal devices based on PTB7-Th:C6OT-4F achieve a preferable efficiency of 9.83% with a low Eloss of 0.47 eV, which is the lowest Eloss among the NFREA-based OSCs with PCE >9% and optoelectronic response over 1000 nm. This work portrays the design concept of ultra-narrow bandgap NFREAs for efficient OSCs as well as low energy loss and exploration of semitransparent photoelectric devices.

High‐Performance Semitransparent Organic Solar Cells Enabled by Improved Charge Transport and Optical Engineering of Ternary Blend Active Layer

Semitransparent organic solar cells (STOSCs) make the industrialization of power‐generating windows a reality with promising average visible transmittance (AVT) and rapidly increased power conversion efficiencies (PCEs). To achieve the ultimate goal, improving the efficiency of STOSCs without degrading the transparency in visible range is critical. Herein, a nonfused ring acceptor (BDC‐4F‐C8) by alkyl chain engineering is used as third component for ternary blend active layer to enhance the electrical and optical properties of STOSCs. With optimizing the proportion of third component, STOSCs with ternary active layer exhibit improved open‐circuit voltage, short‐circuit current, and fill factor, which leads to the best PCE of 13.19% with AVT of 24.56%, while the PCE of opaque one is 17.02%. This work presents an effective strategy to achieve high‐performance ternary STOSCs with high AVT employing a low‐cost nonfused ring electron acceptor material, and manifests how the third component affects the optical features of a ternary active layer to achieve efficient semitransparent devices.

Fluorinated Perylene Diimide Dimer for Organic Solar Cells as Non‐fullerene Acceptor

AbstractFluorination has been widely applied in modification of photovoltaic materials, especially fused ring electron acceptors and polymer donors, but rarely in perylene diimides (PDIs)‐based acceptors. The di‐PDI‐2F is facilely obtained by a one‐step synthesis via stannylation/Stille cross‐coupling reaction. Furtherly, we conducted a comparison study between the newly designed fluorinated PDI dimer di‐PDI‐2F and its non‐fluorinated analogue di‐PDI. After fluorination, the energy levels are downshifted, and the absorption spectrum is greatly blue shifted. When paired with a medium band‐gap donor PM6, di‐PDI‐2F based organic solar cells show reduced trap‐assisted and bimolecular recombination as well as better exciton dissociation and charge collection efficiency than that of di‐PDI based ones, thus a greatly enhanced fill factor (FF), together with improved open circuit voltage (Voc) and short circuit current density (Jsc), leading to a superior power conversion efficiency. This fact suggests the potential of fluorination strategy on PDI based acceptors.

Nonfused Ring Electron Acceptors with a Small Side-Chain Difference Lead to Vastly Different Power Conversion Efficiencies: Impact of Aggregation

Nonfused Ring Electron Acceptors with a Small Side-Chain Difference Lead to Vastly Different Power Conversion Efficiencies: Impact of Aggregation

Peculiarities of Oxidative Polymerization of Diarylaminodichlorobenzoquinones.

New oxidative polymerization monomers—diarylaminodichlorobenzoquinones were synthesised by alkylating aniline, m-phenylenediamine and methanilic acid with chloranil. Oxidative polymerization of diarylaminodichlorobenzoquinones was studied for the first time in relation to the concentration of the monomer, acid, and oxidant/monomer ratio. It was found that the synthesized monomers are highly active in the polymerization reaction, and the oxidation rate grows with the increase in the acid concentration. Only one arylamine group is involved in the polymerization reaction. The optimal oxidant/monomer ratio is stoichiometric for one arylamine group, despite the bifunctionality of the monomers. It was shown that the type of the substituent in the aniline ring (electron donor or electron acceptor) determines the growth of the polymer chain and the structure of the resulting conjugated polymers. A mechanism for the formation of active polymerization centers for diarylaminodichlorobenzoquinones was proposed. FTIR-, NMR-, X-ray photoelectron spectroscopy, and SEM were used to identify the structure of the synthesized monomers and polymers. The obtained polymers have an amorphous structure and a loose globular morphology. The frequency dependence of the electrical conductivity was studied.

Simple Nonfused Ring Electron Acceptors with 3D Network Packing Structure Boosting the Efficiency of Organic Solar Cells to 15.44%

AbstractThree nonfused ring electron acceptors (NFREAs; 2Th‐2F, BTh‐Th‐2F, and 2BTh‐2F) with thieno[3,2‐b]thiophene bearing two bis(4‐butylphenyl)amino substituents as the core, 3‐octylthiophene or 3‐octylthieno[3,2‐b]thiophene as the spacer, and 3‐(1,1‐dicyanomethylene)‐5,6‐difluoro‐1‐indanone as the terminal group are designed and synthesized. The molar extinction coefficient of acceptors and the electron mobility of blend films gradually increase with increasing π‐conjugation length. Moreover, 2BTh‐2F displays a planar molecular conformation assisted by S···N and S···O intramolecular interactions. More importantly, the molecular stacking changes from 2D packing for the 2Th‐2F analog to 3D network packing for 2BTh‐2F. Due to these comprehensive merits, 2BTh‐2F:PBDB‐T‐based organic solar cells give a high power conversion efficiency of 14.53%. More impressively, when D18 is used as the donor polymer, the power conversion efficiency is further enhanced to 15.44%, which is the highest value reported for solar cells based on NFREAs.

High-Performance Simple Nonfused Ring Electron Acceptors with Diphenylamino Flanking Groups.

Four simple nonfused ring electron acceptors (H-2F, CH3-2F, OCH3-2F, and SCH3-2F) were designed and synthesized. The use of diphenylamine derivatives as the flanking group for the construction of nonfused ring electron acceptors can improve solubility, avoid the formation of oversized aggregates, and enhance the intramolecular charge-transfer effect to extend absorption spectra. The substituent group at the diphenylamine unit has a great impact on the absorption and energy level of acceptors, electron mobility and morphology of blend films. Unlike the other three acceptors, CH3-2F can form ordered molecular stacking and a face-on orientation in the donor/acceptor blend film. A single-crystal analysis demonstrates that CH3-2F can form a two-dimensional electron transport network. Among these four acceptors, CH3-2F-based organic solar cells provide the highest PCE of 12.28%. Our work has demonstrated that triarylamine is a helpful construction unit for low-cost and high efficiency nonfused ring electron acceptors.

Novel W-Shaped Oxygen Heterocycle-Fused Fluorene-Based Non-Fullerene Acceptors: First Theoretical Framework for Designing Environment-Friendly Organic Solar Cells

The increasing demand of energy has expedited the research on developing low-cost and environment-friendly organic solar cells (EFOSCs). The commercial application of non-fullerene-fused ring electron acceptors (FREAs) having the 1,1-dicyanomethylene-3-indanone (IC) end group is limited due to the presence of two highly toxic −C≡N groups. This research projects the first theoretical design and exploration of environment-friendly groups transforming promising end-capped electron acceptor molecules for high-performance environment-friendly organic solar cells. For the first time, we developed FCO-based (acceptor–donor–acceptor (A–D–A)) type, novel W-shaped environment-friendly electron acceptor molecules (W1–W6) by modifying the toxic −C≡N group of FCO (reference synthesized molecule R) with three nontoxic electron-withdrawing (−CF3, −SO3H, −NO2) groups. Frontier molecular orbital (FMO) analysis, density of state (DOS) graphs, electron and hole reorganization energy (λe, λh), open-circuit voltage (Voc), transition energy, transition density matrix (TDM) analysis, and exciton-binding energy values of W1–W6 are computed and compared with those of the recently synthesized highly efficient FCO molecule. Results suggest that the photovoltaic, photophysical, and electronic properties of designed molecules W1–W6 are better than those of R. All developed molecules, especially W6, proved to be the preferable optoelectronic material for EFOSCs owing to their low-energy band gap (2.136 eV), highest λmax values of 709.25 and 792.08 nm in gas and chloroform, respectively, with lowest transition energy (1.75 eV), lowest electron mobility (λe = 0.007657 Eh) and hole mobility (λh = 0.006385 Eh), lowest binding energy (Eb = 0.072 eV), and 1.743 V value for open-circuit voltage (Voc) as compared to reference R as well as other developed molecules. Charge transfer analysis among the W6:PM6 blend proved the superposition of orbitals and successful transfer of charge from the highest occupied molecular orbital (HOMO) (PM6) to the lowest unoccupied molecular orbital (LUMO) (W6). Thus, the developed molecules (W1–W6) depicting outstanding optoelectronic properties are recommended as the best nontoxic alternative materials for developing efficient and environment-friendly organic solar cells.

High-performance and low-energy loss organic solar cells with non-fused ring acceptor by alkyl chain engineering

• Alkyl chain engineering is used in non-fused ring acceptor to tune the optoelectronic properties of materials. • The effect of alkyl side chain length on physicochemical and optoelectronic properties are systematically investigated. • A power conversion efficiency of 12.53% with low energy loss of 0.51 eV is achieved. • A relatively low energetic disorder with Urbach energy of 24.01 meV is obtained. Non-fused ring electron acceptors are attractive for organic solar cell (OSC) due to synthetic simplicity and availability of diverse building blocks. However, it is challenging to afford both high-performance and low-energy loss ( E loss ) OSC based on the non-fused ring electron acceptors. Herein, two simple electron acceptors, BDC-4F-C6 and BDC-4F-C8 with non-fused backbones are designed and synthesized by comprising a 5,7-bis(2-ethylhexyl)-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-4,8-dione core, doubly endcapped by fluorinated 1,1-dicyanomethylene-3-indanone terminals through 4H-cyclopenta[1,2-b:5,4-b′]dithiophene bridge. The effects of bridge alkyl side chain length on physicochemical properties and on optoelectronic properties are systematically investigated. Compared with the BDC-4F-C6, BDC-4F-C8 shows a blue-shifted absorption and an elevated LUMO level, which is beneficial for boosting V oc . As a result, a decent power conversion efficiency of 12.53% with a remarkable low E loss of 0.51 eV has been achieved for BDC-4F-C8-based OSCs. It is worth pointing out that E loss of 0.51 eV is the lowest ever reported among highly efficient OSCs based on non-fused ring electron acceptors. Our work demonstrates the effectiveness of side chain engineering of non-fused ring electron acceptors for achieving higher PCE and lower E loss , holding a bright future on the further improvement of the PCE for high-performance OSCs.

Quantum chemical design of near‐infrared sensitive fused ring electron acceptors containing selenophene as π‐bridge for high‐performance organic solar cells

AbstractEnd‐capped acceptors modification of fused ring electron acceptors (FREAs) is an attractive strategy to boost the optoelectronic and photovoltaic properties of the materials. FREAs are also proven beneficial due to their tremendous applications in organic solar cells (OSCs). Among fused‐ring electronic species, small fullerene‐free FREAs have already been drawn more attention due to their near‐infrared sensitivity and constantly increasing efficiencies. Therefore, we have designed six new FREAs (K1–K6) having selenophene as π‐bridge in between the central alkylated indaceno[1,2‐b:5,6b]dithiophene (IDT) unit after the incorporations of various end‐capped acceptors on to the recently synthesized IDT2SeC2C4‐4F molecule. Structural–property relationship and photophysical and photovoltaic properties of newly designed molecules are studied with the help of density functional theory (DFT) and time‐dependent DFT (TD‐DFT). Certain critical specifications like frontier molecular orbitals (FMOs) alignment, density of states (DOS), absorption maxima, excitation energy, binding energy (BE) along with transition density matrix (TDM), and the specifically estimated reorganizational energy values of electron and hole and the open circuit voltages of newly designed molecules are computed and compared with reference molecule. Generally, a red‐shifting absorption behavior of FREAs is considered the most important reason for their high efficiencies in OSCs. Our novel designed molecules exhibit red shift in absorption spectrum. Similarly, low excitation and binding energies of designed molecules offer improved power conversion efficiencies (PCEs) with highest possible charge photocurrent density (Jsc) in OSCs devices. Furthermore, study of PTB7‐Th/K1 complex is also done in order to examine charge transfer between within complex. By introducing the efficient end‐capped acceptor moieties in reference molecule, enhancement in charge mobilities is noted. The large open circuit voltage, low reorganizational energies, narrower highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) energy gap, lower binding and excitation energies, and highly red shifting in absorption phenomenon indicate an efficient designing of molecules, which could be best fitted for high efficiency OSCs. Finally, theorized molecules are much superior related to their photovoltaic and electronic properties and thus are recommended to experimentalist for their synthesis and out‐looking future developments of highly efficient solar cells devices.

Electron-deficient diketone unit engineering for non-fused ring acceptors enabling over 13% efficiency in organic solar cells

A strategy has been developed for incorporating electron-deficient diketone units into efficient non-fused ring electron acceptors via noncovalent interactions to achieve a high-performance OSC with PCE over 13.3%.

Improving the performance of organic solar cells by side chain engineering of fused ring electron acceptors

The side chain engineering of photoactive materials is one of the most commonly used molecular design strategies for developing high performance organic solar cells (OSCs).

Highly efficient fused ring electron acceptors based on a new undecacyclic core

Two FREAs, IUIC-O and IUIC-T, based on a large fused ring donor core (undecacyclic unit) were developed. IUIC-T, having 2D conjugated side chains, affords a higher PCE of 13.05%.

Effects of Fluorination on Fused Ring Electron Acceptor for Active Layer Morphology, Exciton Dissociation, and Charge Recombination in Organic Solar Cells.

Fluorination is one of the effective approaches to alter the organic semiconductor properties that impact the performance of the organic solar cells (OSCs). Positive effects of fluorination are also revealed in the application of fused ring electron acceptors (FREAs). However, in comparison with the efforts allocated to the material designs and power conversion efficiency enhancement, understanding on the excitons and charge carriers' behaviors in high-performing OSCs containing FREAs is limited. Herein, the impact of fluorine substituents on the active layer morphology, and therefore exciton dissociation, charge separation, and charge carriers' recombination processes are examined by fabricating OSCs with PTO2 as the donor and two FREAs, O-IDTT-IC and its fluorinated analogue O-IDTT-4FIC, as the acceptors. With the presence of O-IDTT-4FIC in the devices, it is found that the excitons dissociate more efficiently, and the activation energy required to split the excitons to free charge carriers is much lower; the charge carriers live longer and suffer less extent of trap-assisted recombination; the trap density is 1 order of magnitude lower than that of the nonfluorinated counterpart. Overall, these findings provide information about the complex impacts of FREA fluorination on efficiently performed OSCs.

Insights into out-of-plane side chains effects on optoelectronic and photovoltaic properties of simple non-fused electron acceptors

Non-fused ring electron acceptors with varied substituents were developed to construct efficient organic solar cells (OSCs). Out-of-plane rigid substituents such as 2-methylphenyl, 2-tert-butylphenyl and diphenylamine were introduced to the central benzene unit to improve the solubility of non-fused ring acceptors and noncovalent interactions such as O⋯S and N⋯S were used to enhance the planarity of molecular backbones. Blend films based on PBDB-T and these acceptors displayed better morphology without oversized aggregates formed. As-cast devices based on SM1, SM2 and SM3 exhibited power conversion efficiencies of 5.96%, 6.43% and 6.80%, respectively.

A Fully Non‐fused Ring Acceptor with Planar Backbone and Near‐IR Absorption for High Performance Polymer Solar Cells

AbstractFused‐ring electron acceptors have made significant progress in recent years, while the development of fully non‐fused ring acceptors has been unsatisfactory. Here, two fully non‐fused ring acceptors, o‐4TBC‐2F and m‐4TBC‐2F, were designed and synthesized. By regulating the location of the hexyloxy chains, o‐4TBC‐2F formed planar backbones, while m‐4TBC‐2F displayed a twisted backbone. Additionally, the o‐4TBC‐2F film showed a markedly red‐shifted absorption after thermal annealing, which indicated the formation of J‐aggregates. For fabrication of organic solar cells (OSCs), PBDB‐T was used as a donor and blended with the two acceptors. The o‐4TBC‐2F‐based blend films displayed higher charge mobilities, lower energy loss and a higher power conversion efficiency (PCE). The optimized devices based on o‐4TBC‐2F gave a PCE of 10.26 %, which was much higher than those based on m‐4TBC‐2F at 2.63 %, and it is one of the highest reported PCE values for fully non‐fused ring electron acceptors.

A Fully Non-fused Ring Acceptor with Planar Backbone and Near-IR Absorption for High Performance Polymer Solar Cells.

Fused-ring electron acceptors have made significant progress in recent years, while the development of fully non-fused ring acceptors has been unsatisfactory. Here, two fully non-fused ring acceptors, o-4TBC-2F and m-4TBC-2F, were designed and synthesized. By regulating the location of the hexyloxy chains, o-4TBC-2F formed planar backbones, while m-4TBC-2F displayed a twisted backbone. Additionally, the o-4TBC-2F film showed a markedly red-shifted absorption after thermal annealing, which indicated the formation of J-aggregates. For fabrication of organic solar cells (OSCs), PBDB-T was used as a donor and blended with the two acceptors. The o-4TBC-2F-based blend films displayed higher charge mobilities, lower energy loss and a higher power conversion efficiency (PCE). The optimized devices based on o-4TBC-2F gave a PCE of 10.26 %, which was much higher than those based on m-4TBC-2F at 2.63 %, and it is one of the highest reported PCE values for fully non-fused ring electron acceptors.

Designing alkoxy-induced based high performance near infrared sensitive small molecule acceptors for organic solar cells

Scientist are dedicated to design and synthesize efficient photovoltaic materials to overcome the energy crises. In this regard, herein, we have designed four new small acceptor molecules namely ( A1, A2, A3 and A4 ) for better performance in organic solar cells. These molecules consist Alkoxy-Induced Naphtho-dithiophene core unit flanked with 2,2-ethylidene-5,6-dicyano-3-oxo-2,3-dihydroinden-1-ylidene-malononitrile ( A1 ), methyl-2-cyano-2,2-ethylidene-5,6-difluoro-3-oxo-2,3-dihydroinden-1-ylidene-acetate ( A2 ), 5,2-ethylidene-5,6-difluoro-3-oxo-2,3-dihydroinden-1-ylidene-3-methyl-2-thioxothiazolidin-4-one ( A3 ) and 2,5-ethylidene-6-oxo-5,6-dihydrocyclopenta-thiophen-4-ylidene-malononitrile ( A4 ) end-capped acceptor groups. Their optical, electrical and geometries have been compared with reported molecule R. Frontier molecular orbital diagram reveal excellent charge transfer rate, The electron density is shifted from donor to acceptor unit. Among all, A1 exhibits the highest absorption in the visible region (λ max ) at 798 nm in chloroform solvent. The maximum open circuit voltage (2.08 V) is observed for A3 when blended with PTB7-Th donor polymer. All studied molecules have high charge mobilities due to lower reorganization energy values with respect to model molecule R . A1 has the highest electron mobility among all molecules due to lower value of reorganization energy which is 0.0034. Furthermore, all designed molecules show good Solubilities in organic solvent. A2 exhibit high value of dipole moment which reveal good solubilities in fabrication process. We have designed four ( A1, A2, A3 and A4 ) fused ring electron acceptor for their use in OSCs. These molecules contain Alkoxy-Induced Naphtho-dithiophene core unit attached with different acceptor groups to enhance PCE of OSCs. All newly designed molecule have better performance as compared to R . Additionally, A1 exhibits strong absorption in visible region in both gas phase (λ max = 724.1 nm) and solvent (λ max = 798.4 nm) and exhibit lowest energy band gap (1.92 eV). • A1 shows the highest absorption maximum (λ max ) 798.4 nm in chloroform solvent. • The Designed molecules are blended with well-known donor polymer PTB7-Th. • All designed molecules have lower binding energy as compared to reference molecule R. • All newly designed molecules have excellent opto-electronic properties with respect to R.