Triphenylamine-thienylenevinylene hybrid systems with internal charge transfer as donor materials for heterojunction solar cells

Star-shaped molecules based on a triphenylamine core derivatized with various combinations of thienylenevinylene conjugated branches and electron-withdrawing indanedione or dicyanovinyl groups have been synthesized. UV-vis absorption and fluorescence emission data show that the introduction of the electron-acceptor groups induces an intramolecular charge transfer that results in a shift of the absorption onset toward longer wavelengths and a quenching of photoluminescence. Cyclic voltammetry shows that all compounds present a reversible first oxidation process whose potential increases with the number of electron-withdrawing groups in the structure. Prototype bulk and bilayer heterojunction solar cells have been realized using fullerene C60 derivatives as acceptor material. The results obtained with both kinds of devices show that the introduction of electron-acceptor groups in the donor structure induces an extension of the photoresponse in the visible spectral region, an increase of the maximum external quantum efficiency, and an increase of the open-circuit voltage under white light illumination. These synergistic effects allow reaching power conversion efficiencies of approximately 1.20% under simulated AM 1.5 solar irradiation at 100 mW cm(-2).     

Synthesis and properties of a star-shaped organic material with triphenylamine and N-vinyl carbazole units

A starburst triphenylamine cored N-vinyl carbazole (V-Cz) branched compound was designed and synthesized via optimized Heck reaction in a yield of 40-60%.Moderate yield came from decomposition of V-Cz and self-coupling of triiodo-triphenylamine. TCz-TPA adopts a highly twisted propeller conformation by molecular mechanical optimization.It is readily soluble for its highly twisted conformation.Transparent and pinhole free films could be easily fabricated by spin-coating for its starburst structure.It emits blue-greenish light in CH_2Cl_2 peaked at 460 nm with a narrow full-width at half-maximum (FWHM) of 65 nm.As compared, the absorption peaks of the spin-coated film blue shifted and emission peak red shifted to 510 nm with a FWHM of 96 nm.     

Panchromatic push-pull chromophores based on triphenylamine as donors for molecular solar cells

Two new push-pull chromophores based on triphenylamine as donor and 2-carboxymethyl-2-cyanomethylenethiazole as acceptor have been synthesized. Both exhibit strong light absorption covering from 300 to 800 nm. Electrochemical studies show HOMO-LUMO gaps of 2.01 and 1.54 eV, making, together with the panchromatic absorption, these systems promising materials in the field of molecular photovoltaic devices.     

A star-shaped oligothiophene end-capped with alkyl cyanoacetate groups for solution-processed organic solar cells

A star-shaped oligothiophene based on triphenylamine as a core and 2-ethylhexyl cyanoacetate as end groups (S(TPA-3T-CA)) was synthesized. S(TPA-3T-CA) exhibited strong absorption and high hole mobility. Solution-processed solar cells based on S(TPA-3T-CA):PC(71)BM showed a power conversion efficiency of 3.60% and a fill factor of 0.56.     

基于星射状三苯胺敏化剂的分子设计

以性能优良的三苯胺星射状分子WD8为母体,通过密度泛函理论方法,探讨了取代基团在不同位置时,对母体分子电子性质、光谱性质和电荷传输性能的影响.结果表明,取代基团位置的不同,对分子的前线分子轨道组成基本没有影响.当2-氰基-3-呋喃基-丙烯酸基团取代位置由对位变为间位时,分子的吸收范围最大.当2-氰基-3-呋喃基-丙烯酸基团和1个吩噻嗪-苯基团取代位置由对位变为间位时,分子的EHOMO最大,ELUMO和Eg最小,分子的最大吸收波长最长.当2-氰基-3-呋喃基-丙烯酸基团和2个吩噻嗪-苯基团取代位置由对位变为间位时,分子的电荷传输性能最强.     

Y-shaped dyes based on triphenylamine for efficient dye-sensitized solar cells

Three new triphenylamine-based dyes with Y-shaped conformation bearing triphenylamino-vinyl, 10-octyl-10H-phenothiazine-vinyl and 9-octyl-9H-carbazole-vinyl as arms (TT, TP, and TC) have been synthesized. From electrochemical investigations it is found that they can be employed in DSSCs due to the balanced HOMO and LUMO energy levels. Notably, the photo-to-electrical conversion efficiency of the DSSCs sensitized with branched TT, TP, and TC reach 5.12%, 4.84%, and 3.63%, which are higher than that sensitized with T (2.79%), and the DSSC sensitized with TT shows higher IPCE response and better photovoltaic performances (J_sc=12.37 mA/cm², V_oc=0.72 V and ff=0.58) than others. These results reveal that the introduction of branched Y-shaped extended π-conjugated donors to D-π-A dyes cannot only enlarge the spectral response range, but also suppress the molecular aggregation on TiO₂ films to a certain extent, which would enhance the performance of DSSCs.     

Macrocyclic triphenylamine based organic dyes for efficient dye-sensitized solar cells

A novel class of organic D-π-A dyes employing macrocyclic triphenylamine dimer as electron donor was designed and synthesized for dye-sensitized solar cells. The prepared compounds showed high chemical and elelctrochemical stabilities as well as good long-wave absorption. Photovoltaic devices based on these dyes showed high open circuit voltage (higher than that of N3) and achieved a solar energy to electricity conversion efficiency of 6.31%. All the performances indicate the dyes containing macrocyclic triphenylamine dimer is a good candidate for dyes sensitized solar cells.     

Titanylphthalocyanine as hole transporting material for perovskite solar cells

Titanylphthalocyanine(TiOPc) as hole transporting material(HTM) was successfully synthesized by a simple process with low cost. Perovskite solar cells using the TiOPc as HTM were fabricated and characterized. TiOPc as HTM plays an important role in increasing the power conversion efficiency(PCE) by minimizing recombination losses at the perovskite/Au interface because TiOPc as HTM can extract photogenerated holes from the perovskite and then transport quickly these charges to the back metal electrode. In the research, the β-TiOPc gives a higher PCE than α-TiOPc for the devices due to sufficient transfer dynamics. The β-TiOPc was applied in perovskite solar cells without dopping to afford an impressive PCE of 5.05% under AM 1.5G illumination at the thickness of 40 nm which is competitive with spiro-OMe TAD at the same condition. The present work suggests a guideline for optimizing the photovoltaic properties of perovskite solar cells using the TiOPc as the HTM.     

Planar core based starburst triphenylamine molecules as hole transporting materials for high-performance perovskite solar cells

<正>Starburst triphenylamine molecules are generally used as hole transporting materials (HTMs) for optoelectronic devices like solar cells, light emitting diode and field effect transistors [1]. The use of starburst triphenylamine molecules like spiro-OMeTAD HTM initiated the construction of solid state perovskite solar cells (PSCs)[2,3]. Currently, based on triphenylamine HTMs, the highest power conversion efficiency (PCE) of PSCs is up to 22.1%[4]. Nowadays, spiro-     

A naphthodithiophene-diketopyrrolopyrrole donor molecule for efficient solution-processed solar cells

We report the synthesis, characterization, and first implementation of a naphtho[2,3-b:6,7-b']dithiophene (NDT)-based donor molecule in highly efficient organic photovoltaics (OPVs). When NDT(TDPP)(2) (TDPP = thiophene-capped diketopyrrolopyrrole) is combined with the electron acceptor PC(61)BM, a power conversion efficiency (PCE) of 4.06 ± 0.06% is achieved-a record for a PC(61)BM-based small-molecule OPV. The substantial PCE is attributed to the broad, high oscillator strength visible absorption, the ordered molecular packing, and an exceptional hole mobility of NDT(TDPP)(2).     

Oligomeric donor with appropriate crystallinity for organic solar cells

Improving the performance of all-small-molecule organic solar cells(ASM-OSCs) largely depends on the design and application of novel donors with appropriate crystallinity. Extending molecular conjugation is an effective method for regulating molecular stacking and crystallinity. In this work, we successfully designed and synthesized two novel acceptor-donor-donor-donor-acceptor(A-D-D-D-A) type oligomeric donors with three dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b’]dithiophene(DTBDT) as the centr...     

Metal-free organic dyes with benzothiadiazole as an internal acceptor for dye-sensitized solar cells

We synthesized three metal-free organic dyes (H11–H13) consisting of a 3,6-disubstituted carbazole, benzothiadiazole, and cyanoacrylic acid. All the dyes exhibited high molar extinction coefficients and suitable energy levels for electron transfer from the electrolyte to the TiO₂ nanoparticles. Under standard AM 1.5G solar irradiation, the device using dye H13 with co-adsorbed chenodeoxycholic acid (CDCA) displayed the best performance: an open-circuit voltage (V_oc) of 0.71 V, a short-circuit current density (J_sc) of 12.69 mA cm⁻², a fill factor (FF) of 0.71, and a power conversion efficiency (PCE) of 6.32%. The PCE was ∼79% of that for commercially available N719 cells (8.02%) under the same conditions.     

Materials for organic solar cells: the C60/pi-conjugated oligomer approach

This tutorial review surveys recent advances in the field of C60/pi-conjugated oligomer donor-acceptor ensembles. In particular, different synthetic strategies are discussed that were developed to link pi-conjugated oligomers, as versatile photoexcited state electron donors, to C60. We highlight relationships between the nature/structural aspects of pi-conjugated donor systems and a variety of physico-chemical features. Modifications of the oligomeric components are discussed under aspects of tailoring (i) the absorption cross-section of the chromophore in the visible region, (ii) the oxidation potential of the oligomeric donor moiety, (iii) the size, shape, or chemical makeup of the oligomer, and (iv) the stabilization of the charge-separated radical ion pairs. In the final section, the applicability of selected materials for the fabrication of photovoltaic devices is analyzed.     

A crosslinked polymer as dopant-free hole-transport material for efficient n-i-p type perovskite solar cells

A new crosslinked polymer,called P65,with appropriate photo-electrochemical,opto-electronic,and thermal properties,has been designed and synthesized as an efficient,dopant-free,hole-transport material(HTM)for n-i-p type planar perovskite solar cells(PSCs).P65 is obtained from a low-cost and easily synthesized spiro[fluorene-9,90-xanthene]-30,60-diol(SFX-OH)-based monomer X65 through a freeradical polymerization reaction.The combination of a three-dimensional(3 D)SFX core unit,holetransport methoxydiphenylamine group,and crosslinked polyvinyl network provides P65 with good solubility and excellent film-forming properties.By employing P65 as a dopant-free hole-transport layer in conventional n-i-p type PSCs,a power conversion efficiency(PCE)of up to 17.7%is achieved.To the best of our knowledge,this is the first time a 3 D,crosslinked,polymeric dopant-free HTM has been reported for use in conventional n-i-p type PSCs.This study provides a new strategy for the future development of a 3 D crosslinked polymeric dopant-free HTM with a simple synthetic route and low-cost for commercial,large-scale applications in future PSCs.     

Theoretical investigation of triphenylamine dye/titanium dioxide interface for dye-sensitized solar cells

The structural, electronic and optical features of two metal-free triphenylamine (TPA) organic dyes (namely C206 and C217) before and after binding to a TiO(2) anatase nanoparticle have been investigated in detail, as a model for the corresponding dye-sensitized solar cells (DSSCs). The combination of density functional tight-binding (DFTB), density functional theory (DFT), and time-dependent DFT (TDDFT) approaches are employed. To understand the effects of the linker part in the TPA organic dyes on the energy conversion efficiency of the DSSCs, C217 and C206, which share the same donor and anchor parts but different linker parts, are theoretically evaluated. Our results show that compared with C206 containing just one thienothiophene unit as the linker, for C217 the introduction of one electron-rich 3,4-ethylenedioxythiophene group to the linker part results in stronger couplings with the TiO(2) conduction band and more efficient electron transfer. This difference contributes to the higher efficiency of C217 in DSSCs experiments. This study is expected to assist the molecular design of new and more efficient TPA-based organic dyes for the optimization of the DSSCs.     

Electrodeposition of porous CuSCN layers as hole-conducting material for perovskite solar cells

One of the most promising among hole-conducting materials, CuSCN, was prepared for the first time in a form of porous layers for potential applications in inverted perovskite solar cells.     

A new quinoxaline and isoindigo based polymer as donor material for solar cells: Role of ecofriendly processing solvents on the device efficiency and stability

A new semiconducting polymer based on two different electron deficient (quinoxaline and isoindigo) and electron rich (benzodithiophene) moieties is synthesized, characterized and used as donor material for photovoltaic devices. Blade‐coated bulk heterojunction solar cells are fabricated in air by using chlorinated (o‐dichlorobenzene) and nonchlorinated (o‐xylene) solvents for the deposition of the active layer. The use of o‐xylene allows a ～10% improvement of the device efficiency in comparison to the analogous system processed from o‐dichlorobenzene. In addition, the evolution of the photovoltaic parameters of the resulting devices during thermal stress is monitored and compared, demonstrating a nearly identical resistance against temperature. The reported results not only highlight the promising properties of the new polymer in terms of environmental stability and compatibility with nonhalogenated solvents, but also show an easy and ecofriendly way to further improve the device performance without altering the corresponding thermal stability. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 234–242     

A 3D star-shaped non-fullerene acceptor for solution-processed organic solar cells with a high open-circuit voltage of 1.18 V

A novel 3D star-shaped acceptor based on triphenylamine as a core and diketopyrrolopyrrole as arms (S(TPA-DPP)) was synthesized. S(TPA-DPP) exhibited excellent thermal stability, strong absorption, and very high open-circuit voltage (1.18 V) in solution-processed organic solar cells based on P3HT:S(TPA-DPP).     

Alkoxy substituted benzodithiophene-alt-fluorobenzotriazole copolymer as donor in non-fullerene polymer solar cells

A new benzodithiophene(BDT)-alt-fluorobenzotriazole(FBTA) D-A copolymer J40 was designed and synthesized by introducing 2-octyldodecyloxy side chains on its BDT units, for expanding the family of the BDT- alt-FBTA-based copolymers and investigating the side chain effect on the photovoltaic performance of the polymer in non-fullerene polymer solar cells(PSCs).J40 exhibits complementary absorption spectra and matched electronic energy levels with the n-type organic semiconductor(n-OS)(3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-sindaceno[1,2-b:5,6-b′]dithiophene)(ITIC) acceptor, and was used as polymer donor in the non-fullerene PSCs with ITIC as acceptor. The power conversion efficiency(PCE) of the PSCs based on J40:ITIC(1:1, w/w) with thermal annealing at 120 °C for 10 min reached 6.48% with a higher open-circuit voltage(Voc) of 0.89 V. The high Voc of the PSCs is benefitted from the lower-lying highest occupied molecular orbital(HOMO) energy level of J40. Although the photovoltaic performance of the polymer J40 with alkoxy side chain is lower than that of J60 and J61 with alkylthio-thienyl conjugated side chains, the PCE of6.48% for the J40-based device is still a relatively higher photovoltaic efficiency in the non-fullerene PSCs reported so far. The results indicate that the family of the BDT-alt-FBTA-based D-A copolymers are high performance polymer donor materials for non-fullerene PSCs and the side chain engineering plays an important role in the design of high performance polymer donors in the non-fullerene PSCs.     

Dithienogermole as a fused electron donor in bulk heterojunction solar cells

We report the synthesis and bulk heterojunction photovoltaic performance of the first dithienogermole (DTG)-containing conjugated polymer. Stille polycondensation of a distannyl-DTG derivative with 1,3-dibromo-N-octyl-thienopyrrolodione (TPD) results in an alternating copolymer which displays light absorption extending to 735 nm, and a higher HOMO level than the analogous copolymer containing the commonly utilized dithienosilole (DTS) heterocycle. When polyDTG-TPD:PC(70)BM blends are utilized in inverted bulk heterojunction solar cells, the cells display average power conversion efficiencies of 7.3%, compared to 6.6% for the DTS-containing cells prepared in parallel under identical conditions. The performance enhancement is a result of a higher short-circuit current and fill factor in the DTG-containing cells, which comes at the cost of a slightly lower open circuit voltage than for the DTS-based cells.