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1.
Artigo em Inglês | MEDLINE | ID: mdl-33797187

RESUMO

Despite the remarkable progress being achieved in recent years, organic photovoltaics (OPVs) still need working to approach the balance among the efficiency-stability-cost correlation. Herein, two fully non-fused electron acceptors, PTB4F and PTB4Cl are developed via two-step synthesis from single aromatic units. The introduction of two-dimensional chain and halogenated terminals for these non-fused acceptors plays synergistic roles in optimizing their solid stacking and orientation, thus promoting an elongated exciton lifetime and fast charge transfer rate in bulk heterojunction (BHJ) blends. As results, PTB4Cl, upon blending with PBDB-TF polymer, has enabled single-junction OPVs with power conversion efficiencies of 12.76%, representing the highest values among the reported fully non-fused ring electron acceptors so far.

2.
ACS Nano ; 2021 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-33810640

RESUMO

Organic spacers play an important role in 2D/3D hybrid perovskites, which could combine the advantages of high stability of 2D perovskites and high efficiency of 3D perovskites. Here, a class of aromatic formamidiniums (ArFA) was developed as spacers for 2D/3D perovskites. It is found that the bulky aromatic spacer ArFA in 2D/3D perovskites could induce better crystalline growth and orientation, reduce the defect states, and enlarge spatially resolved carrier lifetime thanks to the multiple NH···I hydrogen-bonding interactions between ArFA and inorganic [PbI6]4- layers. As a result, compared to the control device with efficiency of 19.02%, the 2D/3D perovskite device based on such an optimized organic salt, namely benzamidine hydrochloride (PhFACl), exhibits a dramatically improved efficiency of 22.39% along with improved long-term thermal stability under 80 °C over 1400 h. Importantly, a champion efficiency of 23.36% was further demonstrated through device engineering for PhFACl-based 2D/3D perovskite solar cells. These results indicate the great potential of this class of ArFA spacers in highly efficient 2D/3D perovskite solar cells.

3.
J Phys Chem Lett ; : 3373-3378, 2021 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-33784108

RESUMO

Coexistence of rotationally π-π stacked columns and discrete slip-stacked dimers of perylene bisimide (PBI) chromophores is revealed by single crystal X-ray diffraction in the lamellar crystal of a head-to-tail linked PBI dyad. The rotary π-π stacked columnar moieties show H-type spectral character with relatively higher excitation energy, while the discrete slip-stacked π-π dimers have J-type spectral behavior with lower excitation energy. The lamellar crystals show relatively low photoluminescence efficiency of 12% at room temperature, while this dramatically increases to ∼90% at low temperature (80 K). Both of the rotary and slip-stacked moieties are emissive, and the nonradiative energy transfer processes between them are suppressed at low temperature, ensuring the highly efficient excimer-like long-lived fluorescence.

4.
Artigo em Inglês | MEDLINE | ID: mdl-33492924

RESUMO

In organic photodetectors, photomultiplication is mainly originated from interfacial and/or bulk charge traps, which induces slow response due to the slow release of trapped charges and strongly limits the optimization of the overall performance. This study has exhibited a remarkable case that the gain (>1) and response speed of the lateral photodetectors are promoted simultaneously and effectively by increasing the trap ratio. For lateral photodetectors with silver nanoparticles and PDPPBTT:PC61BM bulk heterojunction, the gain increases from 12.7 to 19.8 and the fall time decreases from 313.4 to 172.9 ms as the PC61BM ratio increases from 5:1 to 1:1. The lateral photodetector structure with a long electrode distance has been testified to play the key role for simultaneous promotion compared with vertical photodiodes, allowing the charges to trap well in the PC61BM-rich phase at a high PC61BM ratio and accumulation of multiple built-in electric fields. The long channel distance and silver nanoparticles also effectively restrain the increment of dark current with PC61BM loading, resulting in a high detectivity of 1.7 × 1012 Jones under 0.031 mW cm-2 @ 820 nm. It is of great theoretical and practical value for the high-performance photodetectors with simultaneous high photomultiplication and quick response.

5.
Nat Commun ; 11(1): 6005, 2020 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-33243982

RESUMO

In non-fullerene organic solar cells, the long-range structure ordering induced by end-group π-π stacking of fused-ring non-fullerene acceptors is considered as the critical factor in realizing efficient charge transport and high power conversion efficiency. Here, we demonstrate that side-chain engineering of non-fullerene acceptors could drive the fused-ring backbone assembly from a π-π stacking mode to an intermixed packing mode, and to a non-stacking mode to refine its solid-state properties. Different from the above-mentioned understanding, we find that close atom contacts in a non-stacking mode can form efficient charge transport pathway through close side atom interactions. The intermixed solid-state packing motif in active layers could enable organic solar cells with superior efficiency and reduced non-radiative recombination loss compared with devices based on molecules with the classic end-group π-π stacking mode. Our observations open a new avenue in material design that endows better photovoltaic performance.

6.
J Am Chem Soc ; 142(47): 20124-20133, 2020 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-33170682

RESUMO

We designed and synthesized a series of fused-ring electron acceptors (FREAs) based on naphthalene-fused octacyclic cores end-capped by 3-(1,1-dicyanomethylene)-5,6-difluoro-1- indanone (NOICs) using a bottom-up approach. The NOIC series shares the same end groups and side chains, as well as similar fused-ring cores. The butterfly effects, arising from different methoxy positions in the starting materials, impact the design of the final FREAs, as well as their molecular packing, optical and electronic properties, charge transport, film morphology, and performance of organic solar cells. The binary-blend devices based on this NOIC series show power conversion efficiencies varying from 7.15% to 14.1%, due to the different intrinsic properties of the NOIC series, morphologies of blend films, and voltage losses of devices.

7.
ACS Appl Mater Interfaces ; 12(45): 50660-50667, 2020 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-33112591

RESUMO

The ternary strategy has been widely used in high-efficiency organic solar cells (OSCs). Herein, we successfully incorporated a mid-band-gap star-shaped acceptor, FBTIC, as the third component into the PM6/Y6 binary blend film, which not only achieved a panchromatic absorption but also significantly improved the open-circuit voltage (VOC) of the devices due to the high-lying lowest unoccupied molecular orbital (LUMO) of the FBTIC. Morphology characterizations show that star-shaped FBTIC molecules are amorphously distributed in the ternary system, and the finely tuned ternary film morphology facilitates the exciton dissociation and charge collection in ternary devices. As a result, the best PM6/Y6/FBTIC-based ternary OSCs achieved a power conversion efficiency (PCE) of 16.7% at a weight ratio of 1.0:1.0:0.2.

8.
Artigo em Inglês | MEDLINE | ID: mdl-33107179

RESUMO

Synthetic routes for heteroatom-containing polycyclic aromatic hydrocarbons (H-PAHs) with alkyl and aryl substitution are demonstrated. Three H-PAHs, including heteroatom-containing rubicenes (H-rubicenes), angular-benzothiophenes (ABTs), and indenothiophene (IDTs) were successfully synthesized by two key steps, including polysubstituted olefin formation and cyclization. Specifically, ABT and H-rubicenes were comprehensively investigated by single-crystal X-ray diffraction, NMR spectroscopy, UV-vis absorption, cyclic voltammetry, transient absorption, and single-crystal OFET measurements.

9.
J Phys Chem Lett ; 11(18): 7908-7913, 2020 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-32897719

RESUMO

The exciton migration mechanism in organic photovoltaic devices is still an ambiguity owing to the insufficient understanding of molecular arrangement on a microscopic scale. Herein, we reveal the relationship between the molecular stacking modes and exciton migration for a representative fused-ring electron acceptor, namely, ITIC. The precise molecular stacking patterns are extracted, and directional Coulombic couplings are calculated based on the information of a single-crystal structure, which proves the anisotropic character for exciton motion. The theoretical analysis results indicate ultrafast exciton migration along the head-to-tail stacking directions with maximum migration length of 330 nm in the finite lifetime of 1 ns. Experimentally, the exciton diffusion length is determined to be 183 nm by exciton-exciton annihilation measurement. This work reveals head-to-tail type intermolecular stacking induces strong anisotropic Coulombic coupling, leading to the ultrafast and long-range exciton migration in nonfullerene systems.

10.
ACS Appl Mater Interfaces ; 12(37): 41861-41868, 2020 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-32819097

RESUMO

Chemical modification of end groups has proved to be an effective way to design new acceptor-donor-acceptor (A-D-A)-structured nonfullerene acceptors (NFAs) for high-performance organic solar cells (OSCs). Herein, we designed and synthesized two nitro-substituted end groups, N1 and N2. Using the two end groups as A units, two A-D-A acceptors, F-N1 and F-N2, were obtained. It also has been found that the nitro substitution position on end groups affects not only the absorptions and energy levels of the resultant acceptor materials but also their molecular packing behavior and active layer morphologies. In addition, the devices based on the two acceptors showed different energy losses. Power-conversion efficiencies (PCEs) of 10.66 and 11.86% were achieved for F-N1- and F-N2-based devices, respectively. This work reveals that the nitration of end groups is one of the potential strategies for designing high-performance photovoltaic active layer materials.

11.
Adv Mater ; 32(33): e2001470, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32627858

RESUMO

Quasi-2D Ruddlesden-Popper (RP) perovskite solar cells (PSCs) have drawn significant attention due to their appealing environmental stability compared to their 3D counterparts. However, the relatively low power conversion efficiency (PCE) greatly limits their applications. Here, high photovoltaic performance is demonstrated for quasi-2D RP PSCs using 2-thiophenemethylammonium as spacer with nominal n-value of 5, which is based on the stoichiometry of the precursors. The incorporation of formamidinium (FA) in quasi-2D RP perovskites reduces the bandgap and improves the light absorption ability, resulting in enlarged photocurrent and an increased PCE of 16.18%, which is higher than that of reported analogous methylammonium (MA)-based quasi-2D PSC (≈15%). A record high PCE of 19.06% is further demonstrated by using an organic salt, namely, 4-(trifluoromethyl)benzylammonium iodide, assisted crystal growth (OACG) technique, which can induce the crystal growth and orientation, tune the surface energy levels, and suppress the charge recombination losses. More importantly, the devices based on OACG-processed quasi-2D RP perovskites show remarkable environmental stability and thermal stability, for example, the PCE retaining ≈96% of its initial value after storage at 80 °C for 576 h, while only ≈37% of the original efficiency left for FAPbI3 -based 3D PSCs.

12.
Adv Sci (Weinh) ; 7(9): 1903784, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32382488

RESUMO

The concept of bromination for organic solar cells has received little attention. However, the electron withdrawing ability and noncovalent interactions of bromine are similar to those of fluorine and chlorine atoms. A tetra-brominated non-fullerene acceptor, designated as BTIC-4Br, has been recently developed by introducing bromine atoms onto the end-capping group of 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene) malononitrile and displayed a high power conversion efficiency (PCE) of 12%. To further improve its photovoltaic performance, the acceptor is optimized either by introducing a longer alkyl chain to the core or by modulating the numbers of bromine substituents. After changing each end-group to a single bromine, the BTIC-2Br-m-based devices exhibit an outstanding PCE of 16.11% with an elevated open-circuit voltage of V oc = 0.88 V, one of the highest PCEs reported among brominated non-fullerene acceptors. This significant improvement can be attributed to the higher light harvesting efficiency, optimized morphology, and higher exciton quenching efficiencies of the di-brominated acceptor. These results demonstrate that the substitution of bromine onto the terminal group of non-fullerene acceptors results in high-efficiency organic semiconductors, and promotes the use of the halogen-substituted strategy for polymer solar cell applications.

13.
ACS Appl Mater Interfaces ; 12(24): 27425-27432, 2020 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-32466636

RESUMO

Adding an additive is one of the effective strategies to fine-tune active layer morphology and improve performance of organic solar cells. In this work, a binary additive 1,8-diiodooctane (DIO) and 2,6-dimethoxynaphthalene (DMON) to optimize the morphology of PBDB-T:TTC8-O1-4F-based devices is reported. With the binary additive, a power conversion efficiency (PCE) of 13.22% was achieved, which is higher than those of devices using DIO (12.05%) or DMON (11.19%) individually. Comparison studies demonstrate that DIO can induce the acceptor TTC8-O1-4F to form ordered packing, while DMON can inhibit excessive aggregation of the donor and acceptor. With the synergistic effect of these two additives, the PBDB-T:TTC8-O1-4F blend film with DIO and DMON exhibits a suitable phase separation and crystallite size, leading to a high short-circuit current density (Jsc) of 23.04 mA·cm-2 and a fill factor of 0.703 and thus improved PCE.

14.
ACS Appl Mater Interfaces ; 12(18): 20714-20721, 2020 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-32272832

RESUMO

In electrochemistry, the carbazole is generally coupled to dimer but not to polymer. This work has reported that organic electropolymerization (OEP) of 4,4',4″-tri(N-carbazolyl)triphenylamine (TCTA) would form a high cross-linked carbazole polymer by its high activity/reversibility and a synchronous viscosity control. It has significantly improved the OEP film quality of both hole-transporting and electroluminescent layers in organic light-emitting diodes. As a result, the conductivity and power efficiency of the organic light-emitting diodes with TCTA are eight and four times of that without TCTA. A prototype display device with a 1.7 in. monochrome passive matrix of 58 ppi under the driving chip is successfully fabricated with accurate pixel size and uniform electroluminescence, which shows a great potential of OEP in the electroluminescent application.

15.
Adv Mater ; 32(21): e2000645, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32285551

RESUMO

A new fluorinated electron acceptor (FINIC) based on 6,6,12,12-tetrakis(3-fluoro-4-hexylphenyl)-indacenobis(dithieno[3,2-b;2',3'-d]thiophene) as the electron-donating central core and 5,6-difluoro-3-(1,1-dicyanomethylene)-1-indanone as the electron-deficient end groups is rationally designed and synthesized. FINIC shows similar absorption profile in dilute solution to the nonfluorinated analogue INIC. However, compared with INIC, FINIC film shows red-shifted absorption, down-shifted frontier molecular orbital energy levels, enhanced crystallinity, and more ordered molecular packing. Single-crystal structure data show that FINIC molecules pack into closer 3D "network" motif through H-bonding and π-π interaction, while INIC molecules pack into incompact "honeycomb" motif through only π-π stacking. Theoretical calculations reveal that FINIC has stronger electronic coupling and more molecular interactions than INIC. FINIC has higher electron mobilities in both horizontal and vertical directions than INIC. Moreover, FINIC and INIC support efficient 3D exciton transport. PBD-SF/FINIC blend has a larger driving force for exciton splitting, more efficient charge transfer and photoinduced charge generation. Finally, the organic solar cells based on PBD-SF/FINIC blend yield power conversion efficiency of 14.0%, far exceeding that of the PBD-SF/INIC-based devices (5.1%).

16.
Angew Chem Int Ed Engl ; 59(26): 10363-10367, 2020 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-32208545

RESUMO

A photocatalytic system containing a perylene bisimide (PBI) dye as a photosensitizer anchored to titanium dioxide (TiO2 ) nanoparticles through carboxyl groups was constructed. Under solar-light irradiation in the presence of sacrificial triethanolamine (TEOA) in neutral and basic conditions (pH 8.5), a reaction cascade is initiated in which the PBI molecule first absorbs green light, giving the formation of a stable radical anion (PBI.- ), which in a second step absorbs near-infrared light, forming a stable PBI dianion (PBI2- ). Finally, the dianion absorbs red light and injects an electron into the TiO2 nanoparticle that is coated with platinum co-catalyst for hydrogen evolution. The hydrogen evolution rates (HERs) are as high as 1216 and 1022 µmol h-1 g-1 with simulated sunlight irradiation in neutral and basic conditions, respectively.

17.
ACS Appl Mater Interfaces ; 12(4): 4638-4648, 2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-31903738

RESUMO

Three noncovalently fused-ring electron acceptors (FOC6-IC, FOC6-FIC, and FOC2C6-2FIC) are synthesized. Single crystals of FOC6-IC and FOC2C6-2FIC are prepared, and structure analyses reveal that the molecular backbone can be planarized via the formation of the intramolecular noncovalent interactions. These acceptor molecules can be packed closely in the solid state via π-π stacking and static interactions between the central phenylene unit and the terminal group with a distance of 3.3-3.4 Å. Besides, multiple intermolecular noncovalent interactions can be observed in the single crystal structure of the fluorinated acceptor FOC2C6-2FIC, which help increase the crystallinity of acceptors and the charge mobility of the blends. Photovoltaic devices based on FOC2C6-2FIC give a power conversion efficiency of 12.36%, higher than 12.08% for FOC6-FIC and 10.80% for FOC6-IC.

18.
ACS Appl Mater Interfaces ; 11(37): 34151-34157, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31436078

RESUMO

A perylene bisimide functionalized with four 4-carboxyphenoxy substituents at bay area (PBI-COOH) was embedded in sol-gel-derived zinc oxide (ZnO) to fabricate organic-inorganic hybrid photoconductive cathode interlayers (ZnO:PBI-COOH) that can be annealed at a rather low temperature of 120-130 °C as desired for plastic substrates for flexible devices. For these interlayers, the structural defects including oxygen vacancy and residual hydroxy groups are reduced that leads to increased electron mobility, and a photoinduced electron transfer from the organic dopant into the conduction band of ZnO endows the hybrid thin film with relatively higher conductivity when compared to the undoped ZnO thin film. The low-temperature-processed hybrid thin films were applied on indium tin oxide electrodes to produce inverted organic solar cells (OSCs) with power conversion efficiencies of 11.68 and 13.48% when using J71:ITIC and PBDB-T-2Cl:IT4F as active layers, respectively. Finally, flexible OSCs are fabricated on poly(ethylene terephthalate) substrates that maintained stability with relatively high performance after 100 times bending.

19.
J Phys Chem Lett ; 10(16): 4737-4743, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31370396

RESUMO

Two chlorine-substituted isomers, ITIC-2Cl-ß and a-ITIC-2Cl, were synthesized for potential use as nonfullerene acceptors. The two molecules differ in the position of chlorine atoms, leading to symmetric (ITIC-2Cl-ß) and asymmetric (a-ITIC-2Cl) molecular configuration. In single crystals, the two molecules exhibit a completely different arrangement and stacking as derived from X-ray diffraction analysis. Whereas ITIC-2Cl-ß has a linear packing structure, a-ITIC-2Cl forms a 3D interpenetrating network structure with shorter π-π distances and better molecular planarity. Therefore, a high power conversion efficiency of >12% is obtained by a-ITIC-2Cl-based devices. It is ∼10% higher than that of ITIC-2Cl-ß-based devices due to the chlorine substituent effect. Thus the fine-tuning of the Cl-substituted position seems to be a promising strategy to construct a 3D interpenetrating charge transportation network and achieve higher performance organic solar cells (OSCs).

20.
iScience ; 17: 302-314, 2019 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-31323476

RESUMO

The influence caused by the position of the chlorine atom on end groups of two non-fullerene acceptors (ITIC-2Cl-δ and ITIC-2Cl-γ) was intensely investigated. The single-crystal structures show that ITIC-2Cl-γ has a better molecular planarity and closer π-π interaction distance. More importantly, a 3D rectangle-like interpenetrating network is formed in ITIC-2Cl-γ and is beneficial to rapid charge transfer along multiple directions, whereas only a linear stacked structure could be observed in ITIC-2Cl-δ. The two acceptor-based solar cells show power conversion efficiencies (PCEs) over 11%, higher than that of the ITIC-2Cl-m-based device (10.85%). An excellent PCE of 13.03% is obtained by the ITIC-2Cl-γ-based device. In addition, the ITIC-2Cl-γ-based device also shows the best device stability. This study indicates that chlorine positioning has a great impact on the acceptors; more importantly, the 3D network structure may be a promising strategy for non-fullerene acceptors to improve the PCE and stability of organic solar cells.

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