Ultra-high-efficiency capture of lead ions over acetylenic bond-rich graphdiyne adsorbent in aqueous solution.

A satisfactory material with high adsorption capacity is urgently needed to solve the serious problem of environment and human health caused by lead pollution. Herein, hydrogen-substituted graphdiyne (HsGDY) was successfully fabricated and employed to remove lead ions from sewage and lead-containing blood. The as-prepared HsGDY exhibits the highest adsorption capacity of lead among the reported materials with a maximum adsorption capacity of 2,390 mg/g, i.e., ~five times larger than that of graphdiyne (GDY). The distinguished hexagonal hole and stack mode of HsGDY allows the adsorption of more lead via its inner side adsorption mode in one single unit space. In addition, the Pb 6s and H 1s hybridization promotes the strong bonding of lead atom adsorbed at the acetylenic bond of HsGDY, contributing to the high adsorption capacity. HsGDY can be easily regenerated by acid treatment and showed excellent regeneration ability and reliability after six adsorption-regeneration cycles. Langmuir isotherm model, pseudo second order, and density functional theory (DFT) demonstrated that the lead adsorption process in HsGDY is monolayer chemisorption. Furthermore, the HsGDY-based portable filter can handle 1,000 µg/L lead-containing aqueous solution up to 1,000 mL, which is nearly 6.67 times that of commercial activated carbon particles. And, the HsGDY shows good biocompatibility and excellent removal efficiency to 100 µg/L blood lead, which is 1.7 times higher than that of GDY. These findings suggest that HsGDY could be a promising adsorbent for practical lead and other heavy metal removal.

Neighboring sp-Hybridized Carbon Participated Molecular Oxygen Activation on the Interface of Sub-nanocluster CuO/Graphdiyne.

Activation of O2 is a crucial step in oxidation processes. Here, the concept of sp-hybridized C≡C triple bonds as an electron donor is adopted to develop highly active and stable catalysts for molecular oxygen activation. We demonstrate that the neighboring sp-hybridized C and Cu sites on the interface of the sub-nanocluster CuO/graphdiyne are the key structures to effectively modulate the O2 activation process in the bridging adsorption mode. The as-prepared sub-nanocluster CuO/graphdiyne catalyst exhibited the highest CO oxidation activity and readily converted 50% CO at around 133 °C, which is 34 and 94 °C lower than that for CuO/graphene and CuO/active carbon catalysts, respectively. In situ diffused reflectance infrared Fourier transform spectroscopy and density functional theory calculation results proved that the neighboring sp-hybridized C is more favorable to promote the rapid dissociation of carbonate than sp2-hybridized C without overcoming any energy barrier. The gaseous CO directly reacts with the active molecular oxygen and tends to proceed through the E-R mechanism with a relatively low energy barrier (0.20 eV). This work revealed that sp-hybridized C of graphdiyne-based materials could effectively improve the O2 activation efficiency, which could facilitate the low-temperature oxidation processes.

Interfacial sp C-O-Mo Hybridization Originated High-Current Density Hydrogen Evolution.

High-current density (≥1 A cm-2) is a critical factor for large-scale industrial application of water-splitting electrocatalysts, especially seawater-splitting. However, it still remains a great challenge to reach high-current density due to the lack of active and stable intrinsic catalytic active sites in catalysts. Herein, we report an original three-dimensional self-supporting graphdiyne/molybdenum oxide (GDY/MoO3) material for efficient hydrogen evolution reaction via a rational design of "sp C-O-Mo hybridization" on the interface. The "sp C-O-Mo hybridization" creates new intrinsic catalytic active sites (nonoxygen vacancy sites) and increases the amount of active sites (eight times higher than pure MoO3). The "sp C-O-Mo hybridization" facilitates charge transfer and boosts the dissociation process of H2O molecules, leading to outstanding HER activity with high-current density (>1.2 A cm-2) in alkaline electrolyte and a decent activity and stability in natural seawater. Our results show that high-current density electrocatalysts can be achieved by interfacial chemical bond engineering, three-dimensional structure design, and hydrophilicity optimization.

Synthesis and properties of a novel decacyclic S,N-heteroacene.

S,N-Heteroacene materials with fused multicyclic heteroaromatics have become increasingly attractive for organic optoelectronic device applications. In this work, the Cadogan ring-closure reaction between the benzene moiety of thieno[3,2-b]indole and 5,6-dinitrobenzo[c][1,2,5]thiadiazole was employed to prepare the novel decacyclic S,N-heteroacene 15,16-dibutyl-14,17-didodecyldithieno[2'',3'':2',3']indolo[6',7':4,5]pyrrolo[3,2-e:2',3'-g][2,1,3]benzothiadiazole (TIP), C58H76N6S3. The conjugated backbone of TIP is extended in comparison with its octacyclic analogue as the central unit within Y6-type molecular acceptors, a family of overwhelming electron acceptors in polymer solar-cell research. The single-crystal X-ray diffraction (SC-XRD) characterization indicated the existence of π-π and C(sp2)-H...π interactions among TIP molecules. The electrochemical and optical properties of TIP were also characterized. As a novel S,N-heteroacene building block, TIP is anticipated to be of potential use in the construction of promising electronic materials.

Positional isomeric effect of monobrominated ending groups within small molecule acceptors on photovoltaic performance.

As an ending acceptor unit (A) within acceptor-donor-acceptor (A-D-A)-type small molecule acceptors (SMAs), monobrominated 1,1-dicyanomethylene-3-indanone (IC-Br) plays a critical role on developing high-performance SMAs and polymer acceptors from polymerizing SMAs. IC-Br is usually a mixture (IC-Br-m) consisting of positional isomeric IC-Br-γ and IC-Br-δ (bromine substituted on the γ and δ positions, respectively). The positional isomeric effect of these monobrominated ending groups has been witnessed to take an important role on regulating the photovoltaic performance. Fully investigating this isomeric effect of monobromination would be of great value for SMAs and even polymer acceptors. In this study, benefitting from the separation of IC-Br-γ and IC-Br-δ from IC-Br-m with high yields, bis(thieno[3,2-b]cyclopenta)benzo[1,2-b:4,5-b']diselenophene (BDSeT) was chosen as the D unit and combined with IC-Br-γ, IC-Br-δ and IC-Br-m as A units, respectively. Three A-D-A type SMAs (BDSeTICBr-γ, BDSeTICBr-δ and BDSeTICBr-m) have thus been obtained. When blended with the representative donor polymer of PBDB-T-2Cl to construct bulk heterojunction (BHJ) polymer solar cells (PSCs), BDSeTICBr-γ, BDSeTICBr-δ and BDSeTICBr-m devices offered power conversion efficiencies (PCEs) of 9.42, 10.63, and 11.54% respectively. The result indicated the superior photovoltaic performance of the isomer mixture over the pure isomers, which was contrary to the reported ones that the pure isomers of SMAs used to give a better performance. The superior performance of the BDSeTICBr-m devices was mainly reflected in the improved carrier generation and transport as well as the carrier recombination suppression. In the three PBDB-T-2Cl:SMA BHJ films, a comparable intermixing phase and acceptor domain sizes were observed. Compared with BDSeTICBr-γ and BDSeTICBr-δ, BDSeTICBr-m showed a preferential face-on orientated packing with the closest π-π stacking in its BHJ film, probably accounting for its higher photovoltaic performance than those of the pure isomers. This study provides an alternative sight to develop efficient SMAs with suitably monobrominated IC ending groups for the strategy of polymerizing SMAs.

Bis(thieno[3,2-b]thieno)cyclopentafluorene-Based Acceptor with Efficient and Comparable Photovoltaic Performance under Various Processing Conditions.

The morphology of a bulk heterojunction (BHJ) blend within a polymer solar cell (PSC) device plays a crucial role in its performance. The ideal morphology is generally achieved through molecular engineering and optimization under film processing conditions. Under different processing conditions, the deviation of the resulted morphology characteristics from the ideal one leads to the dispersion of device performance. For a specific donor/acceptor BHJ blend, it is of great challenge to maintain an efficient and comparable photovoltaic performance under various processing conditions. The solution to this challenge would be of great value in offering more choices for a suitable processing technology in practical applications. Based on the acceptor BTTFIC with the core of bis(thieno[3,2-b]thieno)cyclopentafluorene (BTTF) in our previous work, we chemically modified BTTFIC by fluorination of the end groups of 1,1-dicyanomethylene-3-indanones (IC) and the switching part of octyls in BTTF with 4-hexylphenyls to offer a novel acceptor (BTTFIC4F-Ar). The inverted PBDB-T-2Cl:BTTFIC4F-Ar blend device provided an average power conversion efficiency (PCE) of 10.61, 11.08, and 11.55% when processed under solvent annealing (SA), thermal annealing (TA), and additive treatment with 1,8-diodooctane (DIO), respectively. Different from the reported discrete performance under various processing conditions for a specific donor/acceptor BHJ blend, a low mean absolute performance deviation of 3% was attained. This slight enhancement trend was unexceptionally reflected on charge generation, transportation, and recombination within the blend films from SA, TA, and DIO conditions. A slightly improved ordering of BTTFIC4F-Ar within the DIO blend was observed. Meanwhile, very similar molecular packings as well as a close amorphous domain size of the mixture of PBDB-T-2Cl and BTTFIC4F-Ar within the three blends were observed. These morphological characteristics are in good agreement with the photoelectrical conversion performance of the blends under the three processing conditions. Furthermore, similar attenuation behaviors in performance were also observed. This investigation may provide new guidance on the molecular engineering of nonfullerene acceptors to achieve an efficient BHJ blend with more options for a suitable and cost-effective processing method in practical applications.

Ladder-Type Nonacyclic Arene Bis(thieno[3,2-b]thieno)cyclopentafluorene as a Promising Building Block for Non-Fullerene Acceptors.

The ladder-type nonacyclic arene (bis(thieno[3,2-b]thieno)cyclopentafluorene (BTTF)) has been designed and synthesized through fusing thienothiophenes with the fluorene core from the synthon of dimethyl 9,9-dioctyl-2,7-bis(thieno[3,2-b]thiophen-2-yl)fluorene-3,6-dicarboxylate. With BTTF as the central donor unit, a novel acceptor-donor-acceptor (A-D-A) type non-fullerene small-molecule acceptor (BTTFIC) was prepared with 1,1-dicyanomethylene-3-indanones (IC) as the peripheral acceptor units. The energy level of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of BTTFIC locate at -5.56 and -3.95 eV, respectively, presenting a low optical band gap of 1.58 eV. Encouragingly, polymer solar cells based on the blends of BTTFIC with both the representative wide- and low-bandgap polymer donors (PBDB-T, 1.82 eV. PTB7-Th, 1.58 eV) offer power conversion efficiencies over 8 % (8.78±0.18 % for PBDB-T:BTTFIC and 8.18±0.29 % for PTB7-Th:BTTFIC). These results highlight the advantage of ladder-type BTTF on the preparation of nonfullerene acceptors with extended conjugated backbones.

Improved Performance of Planar Perovskite Solar Cells Using an Amino-Terminated Multifunctional Fullerene Derivative as the Passivation Layer.

Organic-inorganic metal-halide perovskite solar cells (PSCs) have been revolutionizing the photovoltaic (PV) community in the past decade. However, the trap states in TiO2 as the electron-transport layer seriously affect the device PV performance and stability. Here, we design and synthesize a fullerene derivative C60NH2 featuring an amino-terminated group. We use C60NH2 as a passivation layer between TiO2 and perovskite in planar PSCs with a standard configuration to improve the quality of the obtained perovskite film as well as the electron-transfer efficiency, resulting in an obvious increment of PV performance and stability of the devices. The champion power conversion efficiency of 18.34% is achieved under 100 mW cm-2 illumination utilizing C60NH2 as the passivation layer with much less hysteresis. Planar PSCs demonstrate superior stability under natural sunlight and 40-50% relative humidity after C60NH2 passivation. This work enriches the choices of materials for interface engineering toward fabrication of planar PSCs with high performance.

Molecular Engineering of Conjugated Polymers for Solar Cells: An Updated Report.

The device efficiency of polymer:fullerene bulk heterojunction solar cells has recently surpassed 11%, as a result of synergistic efforts among chemists, physicists, and engineers. Since polymers are unequivocally the "heart" of this emerging technology, their design and synthesis have consistently played the key role in the device efficiency enhancement. In this article, the first focus is a discussion on molecular engineering (e.g., backbone, side chains, and substituents), then the discussion moves on to polymer engineering (e.g., molecular weight). Examples are primarily selected from the authors contributions; yet other significant discoveries/developments are also included to put the discussion in a broader context. Given that the synthesis, morphology, and device physics are inherently related in explaining the measured device output parameters (Jsc , Voc and FF), we will attempt to apply an integrated and comprehensive approach (synthesis, morphology, and device physics) to elucidate the fundamental, underlying principles that govern the device characteristics, in particular, in the context of disclosing structure-property correlations. Such correlations are crucial to the design and synthesis of next generation materials to further improve the device efficiency.

A Ladder-type Heteroheptacene 12H-Dithieno[2',3':4,5]thieno[3,2-b:2',3'-h]fluorene Based D-A Copolymer with Strong Intermolecular Interactions toward Efficient Polymer Solar Cells.

Ladder-type electron-donating units for D-A copolymers applied in polymer solar cells usually comprise multiple tetrahedral carbon bridges bonded with out-of-plane alkyl chains for desirable solubility for device processing. However, molecular packing of resultant copolymers in the solid state and charge transport within devices are also impeded in spite of with multiple fused aromatic backbones. To mitigate this issue, a structurally well-defined ladder-type electron-donating heteroheptacene, 12H-dithieno[2',3':4,5]thieno[3,2-b:2',3'-h]fluorene (DTTF) with an extended conjugated backbone and a single tetrahedral carbon bridge attached with two bulky alkyl chains was designed and synthesized. The copolymerization of DTTF with 4,7-bis(4-hexylthiophen-2-yl)benzo[c][1,2,5]thiadiazole (DTBT) afforded a soluble D-A copolymer (PDTTF-DTBT) with a medium optical band gap of 1.72 eV and low-lying HOMO level at -5.36 eV. PDTTF-DTBT unprecedentedly exhibits strong intermolecular stacking ability and presents preferential face-on orientation on both ZnO and PEDOT:PSS layers. The improved packing order and appropriate phase separation of both the copolymer and PC71BM in the bulk heterojunction blend on the ZnO layer over on the PEDOT:PSS layer lead to much improved power conversion efficiency of ∼8.2% in the inverted solar cell device, among the highest for reported ladder-type D-A copolymers. The research demonstrates that it is an effective method to incorporate a single tetrahedral carbon bridge to the molecular center of a ladder-type heteroacene with heavily extended π-conjugation to prepare D-A copolymers toward highly efficient PSCs.

Dynamics of photoinduced electron transfer in a molecular donor-acceptor quartet.

The electronic structures and dynamics of photoinduced charge separation and recombination in a new donor/acceptor quartet molecule with bis-oligothiophene (BOTH) and bis-perylenediimide (BPDI) blocks attached to a benzene ring were described. Detailed transient spectroscopic studies were carried out on this compound and reference compounds at isolated molecular levels in solution. Two different dynamics of charge separation and recombination associated with two types of donor/acceptor pair conformations in solution were observed. These results were discussed based on Marcus theory and ascribed to both through-bond and through-space electron-transfer processes associated with two different orientations of the acceptors relative to the donor group. This molecular system exhibits a more efficient charge separation than charge recombination processes in both polar and nonpolar organic solvents, indicating that the material is an interesting candidate for photovoltaic studies in solid state.

A method for controlling the synthesis of stable twisted two-dimensional conjugated molecules.

Thermodynamic stabilization (π-electron delocalization through effective conjugation) and kinetic stabilization (blocking the most-reactive sites) are important considerations when designing stable polycyclic aromatic hydrocarbons displaying tunable optoelectronic properties. Here, we demonstrate an efficient method for preparing a series of stable two-dimensional (2D) twisted dibenzoterrylene-acenes. We investigated their electronic structures and geometries in the ground state through various experiments assisted by calculations using density functional theory. We find that the length of the acene has a clear effect on the photophysical, electrochemical, and magnetic properties. These molecules exhibit tunable ground-state structures, in which a stable open-shell quintet tetraradical can be transferred to triplet diradicals. Such compounds are promising candidates for use in nonlinear optics, field effect transistors and organic spintronics; furthermore, they may enable broader applications of 2D small organic molecules in high-performance electronic and optical devices.

Enhancement of Photovoltaic Performance by Utilizing Readily Accessible Hole Transporting Layer of Vanadium(V) Oxide Hydrate in a Polymer-Fullerene Blend Solar Cell.

UNLABELLED: Herein, a successful application of V2O5·nH2O film as hole transporting layer (HTL) instead of PEDOT: PSS in polymer solar cells is demonstrated. The V2O5·nH2O layer was spin-coated from V2O5·nH2O sol made from melting-quenching sol-gel method by directly using vanadium oxide powder, which is readily accessible and cost-effective. V2O5·nH2O (n ≈ 1) HTL is found to have comparable work function and smooth surface to that of PEDOT: PSS. For the solar cell containing V2O5·nH2O HTL and the active layer of the blend of a novel polymer donor (PBDSe-DT2PyT) and the acceptor of PC71BM, the PCE was significantly improved to 5.87% with a 30% increase over 4.55% attained with PEDOT: PSS HTL. Incorporation of V2O5·nH2O as HTL in the polymer solar cell was found to enhance the crystallinity of the active layer, electron-blocking at the anode and the light-harvest in the wavelength range of 400-550 nm in the cell. V2O5·nH2O HTL improves the charge generation and collection and suppress the charge recombination within the PBDSe-DT2PyT:PC71BM solar cell, leading to a simultaneous enhancement in Voc, Jsc, and FF. The V2O5·nH2O HTL proposed in this work is envisioned to be of great potential to fabricate highly efficient PSCs with low-cost and massive production.

Dyads and triads containing perylenetetracarboxylic diimide and porphyrin: efficient photoinduced electron transfer elicited via both excited singlet states.

Synthesis, characterizations, and photophysical properties of new photoactive dyads and triads containing perylenetetracarboxylic diimide (PIm) and porphyrin (free-base porphyrin (H(2)P) and zinc porphyrin (ZnP)), in which both entities were connected with a short ether bond, were examined with the aim of using these systems for molecular photonics. The porphyrin(P)-PIm systems absorbed strongly across the visible region, which greatly matched the solar spectrum. The geometric and electronic structures of the dyads and triads were probed using density function theory method at the B3LYP/3-21G level. It was revealed that the majority of the highest-occupied molecular orbital was located on the porphyrin entity, while the lowest-unoccupied molecular orbitals were entirely on the PIm entity. The excited-state electron-transfer processes were monitored by both steady-state and time-resolved emission as well as transient-absorption techniques in polar solvent benzonitrile. Upon excitation of the P (H(2)P and ZnP) moieties, efficient fluorescence quenching of the P moiety was observed, suggesting that the main quenching paths involved charge separation from the excited singlet porphyrin ((1)P) to the PIm moiety. Upon excitation of the PIm moiety, fluorescence quenching of the (1)PIm moiety was also observed. The nanosecond transience of spectra in near-IR region revealed the charge separation process from the P moieties to the PIm moiety via their excited singlet states. The lifetimes of the charge-separated states were evaluated to be 7-14 ns, depending on the solvent polarity. Photosensitized electron mediation systems were also revealed in the presence of methyl viologen and sacrificial electron donor.

Synthesis and characterization of three novel [60]fullerene derivatives toward self-assembled nanoparticles through interaction of hydrogen bonding.

[structure: see text] Three novel fullerene derivatives bearing a 2,6-bis(acylamino) pyridine unit as a hydrogen bonding motif displaying a dimerization tendency were synthesized and characterized by the cycloaddition reaction of alkyl azide to [60]fullerene. An SEM image of the dimerization system of compound 1 indicated spherical particles having a mean diameter of 15 nm with a rather narrow size distribution.

Self-assembly and characterization of supramolecular [60]fullerene-containing 2,6-diacylamidopyridine with uracil derivative by hydrogen-bonding interaction.

[structure: see text] Novel self-assembly systems of uracil derivatives with organofullerene by a three-point hydrogen-bonding interaction were designed and established. The formation of hydrogen bonding was established by 1H NMR studies in CDCl3.

Self-assembly and characterization of a novel hydrogen-bonded nanostructure.

A novel hydrogen-bonded supramolecular system of a [60]fullerene derivative with perylene bisimide was synthesized and characterized. 1H NMR spectra confirmed the existence of strong hydrogen-bonding interaction between compounds 1 and 5. Transmission electron microscopy images of 1.5 aggregates showed spherical particles having a mean diameter of 50 nm. The photocurrent response of the film was measured, and a steady and rapid anodic photocurrent response was obtained.

BiOX (X=Cl, Br, I) nanostructures: mannitol-mediated microwave synthesis, visible light photocatalytic performance, and Cr(VI) removal capacity.

A facile microwave irradiation method has been successfully developed for the controllable fabrication of BiOX (X=Cl, Br, I) nanostructures in mannitol solution. The morphology and size of BiOX nanostructures could be readily tailored by adjusting the amount of halide, reaction precursor, and mannitol concentration. Mannitol molecule acts as both a capping agent and a cohesive agent in the formation of BiOX nanostructures. A possible two-stage formation mechanism was discussed based on the morphology evolution of BiOI nanostructures obtained in mannitol solution with different concentrations. The as-synthesized BiOX nanostructures exhibit much higher photocatalytic activities than that of commercial TiO2. In particular, flower-like BiOX hierarchical nanostructures display the best photocatalytic performance, which is mainly ascribed to their unique hierarchical structure, high BET surface area, and large band gap. Moreover, BiOX nanostructures also demonstrate superior Cr(VI) removal capacity. The Cr(VI) adsorption behavior was also analyzed by the Langmuir and Freundlich adsorption isotherms.

Synthesis and photovoltaic properties of novel monoadducts and bisadducts based on amide methanofullerene.

Four new [6,6]-phenyl-C(61) and C(71) butylsaure n-dibutyl amides (PCBDBA) with mono- and bis-adduction on C(60) and C(70) cages, respectively, have been synthesized as models to study the effect of the mono- and bis-adduction on fullerene cages on device performance when used as electron acceptors with the donor of regioregular P3HT in bulkheterojunction organic photovoltaics (BHJ-OPV). The optoelectronic, electrochemistry, and photovoltaic properties of these mono- and bis-products were fully investigated. The best device performance of these fullerene derivatives were obtained from the two monoadducts with power conversion efficiency (PCE) of 1.77% for C(60) derivative and 1.90% for C(70) derivative, respectively, which are close to PCBM's 2.43%. The results revealed the structure-function relationship among the monoadduct and bisadduct derivatives of C(60) and C(70) with the BHJ-OPV performance.

Conjugated polymers based on benzo[2,1-b:3,4-b']dithiophene with low-lying highest occupied molecular orbital energy levels for organic photovoltaics.

Fusing bithiophene units with a benzo moiety, benzo[2,1-b:3,4-b']dithiophene (BDT), was projected by theoretical calculations to lower the highest occupied molecular orbital (HOMO) energy level of the resulting polymers compared with that of the bithiophene unit, which would enhance the open circuit voltage of bulk heterojunction photovoltaic cells fabricated from BDT-based polymers blended with PCBM. The homopolymer of BDT (HMPBDT) and alternating copolymer of BDT with 2,1,3-benzothiadiazole (PBDT-BT) were therefore synthesized and fully characterized. Both the homopolymer (HMPBDT) and the copolymer (PBDT-BT) were experimentally confirmed to have low HOMO energy levels (-5.70 eV for HMPBDT and -5.34 eV for PBDT-BT). Introducing the acceptor moiety (2,1,3-benzothiadiazole) successfully lowered the optical band gap of the copolymer from 2.31 eV (HMPBDT) to 1.78 eV (PBDT-BT). Bulk heterojunction photovoltaic devices were fabricated from blends of these structurally related polymers with PBCM to investigate the photovoltaic performances. The optimized device of HMPBDT:PCBM (1:3, 180 nm) exhibited an improved open circuit voltage (V(oc)) of 0.76 V, a short circuit current (J(sc)) of 0.34 mA/cm(2), and a fill factor (FF) of 0.40, offering an overall efficiency of 0.10%. The observed large phase separation of the thin film by AFM and the large band gap were accountable for the small current. The optimized device of PBDT-BT:PCBM (1:3, 55 nm) demonstrated a better efficiency of 0.6%, with V(oc) = 0.72 V, J(sc) = 2.06 mA/cm(2), and FF = 0.42. The much improved current was attributed to the lower bandgap and better film morphology. However, the low hole mobility limited the thickness of the PBDT-BT:PCBM film, making inaccessible the thicker film which would utilize more light and enhance the current. Further improvements are expected if the mobility and film morphology can be improved by the new materials design, together with low band gap and low HOMO energy level.