Efficiency boost significantly of ternary organic solar cells by doping low bandgap polymer

Ternary blends composed of two donor absorbers and a complementary absorbing material provide an opportunity to enhance the short-circuit current and thus improved the power conversion efficiency (PCE) of polymer solar cells (PSCs). The used of PBT-T-DPP as the complementary electron donor in poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyricacid methyl ester (PC₆₁BM) blend to construct the ternary PSCs. The PCE of the optimized ternary blend PSCs (with 5 wt% PBT-T-DPP) reached 3.65%, which was 15.51% higher than that of the PSCs with binary blends of P3HT:PC₆₁BM. The ternary blend with 5 wt% PBT-T-DPP exhibited well-developed morphology while the blend with 15 wt% PBT-T-DPP showed phase separation with large-sized domains. Improved photovoltaic performance of ternary PSCs was mainly due to complementary absorption of two donors as well as facilitating charge separation and transport while suppressing charge recombination through a combination of cascade energy levels and optimized device morphology.     

Bulk Heterojunction Solar Cells with Ternary Mixed PTB7:PCDTBT:PC71BM Active Layers

We report on bulk-heterojunction solar cells fabricated based on ternary mixed solutions of two donors of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo [1,2-b:4,5-b’] dithiophene-2, 6-diyl] [3-fluoro-2- [(2-ethylhexyl) carbonyl]thieno[3,4-b]-thiophenediyl] (PTB7) and [N-9’-heptadecanyl-2,7-carbazole-alt-5,5-(4’,7’-di-2-thienyl-2’,1’,3’-benzothiadiazole)] (PCDTBT), and an accepter of [6,6]-phenyl C₇₁ butyric acid methyl ester (PC₇₁BM). The solar cells had a glass/ITO/NiO/PTB7:PCDTBT:PC₇₁BM/LiF/Al structure. Solar cells containing a 1-2% PCDTBT weight fraction showed a noticeable improvement in short circuit current density (J_sc), fill factor (FF), and power conversion efficiency (PCE). Solar cells with a 2% PCDTBT weight fraction exhibited an open circuit voltage (V_oc) of 0.77 V, J_sc of 13 mA/cm², FF of 0.42, and PCE of 4.23%. Possible mechanisms for the solar cell performance improvement by the introduction of the small amount of PCDTBT in the PTB7:PC₇₁BM active layer was discussed based on the active layer morphology changes and carrier transport mechanisms.     

Spectroscopic Determination of Charge Formation Efficiency of Organic Photovoltaic Cells

The internal quantum efficiency (Φ_IQ) of an organic photovoltaic (OPV) cell is governed by plural processes, i.e., the carrier formation process at the D/A interface and the carrier transfer process toward the collector electrode. Then, Φ_IQ can be decomposed into the carrier formation (Φ_CF) and carrier transfer efficiencies (Φ_CT). By combination of femtosecond time-resolved and electrochemical spectroscopies, we determined absolute values of Φ_CF of F8T2/PC₇₁BM, P3HT/PCBM, and PTB7/PC₇₁BM solar cells. We found that Φ_CF at 400 nm of the F8T2/PC₇₁BM cell is higher than those of the P3HT/PCBM, and PTB7/PC₇₁BM cells, although Φ_IQ at 400 nm is the lowest.     

Morphology of F8T2/PC71BM Blend Film as Investigated by Scanning Transmission X-ray Microscope (STXM)

Clarification of the morphology of bulk heterojunction (BHJ) is indispensable for true comprehension of the organic solar cells. Here, we performed scanning transmission X-ray microscopy (STXM) for a poly-(9,9-dioctylfluorene-co-bithiophene) (F8T2)/[6,6]-phenyl C71-butyric acid methyl ester (PC₇₁BM) blend film annealed at various temperatures (T_an). We found that the fullerene concentration within the polymer-rich domain decreases with T_an while the domain size (～230 nm) is essentially unchanged. We will discuss the interrelation between the film morphology and the photovoltaic performance.     

Solution-processible Cd-doped ZnO nanoparticles as an electron transport layer to achieve high performance polymer solar cells through improve conductivity and light transmittance

Abstract

In this work, electron transport layers (ETLs) with high charge transfer ability were prepared by doping ZnO nanoparticles with different concentrations of cadmium(Cd). The inverted polymer solar cell based on PTB7-Th: PC₇₁BM as active layer and various concentrations Cd-doped ZnO (CZO) as ETLs were fabricated. The PCE of the device with optimized Cd content in the ZnO film was about 14.7% larger than that of the pure ZnO-based cells. The cadmium-doped ZnO(CZO) is a good candidate to be used as a high-quality transparent electrode in solar cell applications.     

Solution-processed small-molecule organic solar cells based on diketopyrrolopyrrole and perlyene derivatives with coplanar structures

ABSTRACT

A series of small-molecules (SMs) based on coplanar perylene unit coupled with diketopyrrolopyrrole chromophoric core exhibit broad absorption in the range of 500–800 nm and low bandgap energise of 1.6–1.7 eV. The power conversion efficiency approximately reach at 0.4% under 1.5 G illumination is achieved for organic solar cells based on a small-molecule bulk heterojunction system consisting of SMs as a donor and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) as an acceptor.     

PL Quenching of Poly(3-hexylthiophene) by 2,2′,7,7′-Tetradiphenylamino-9,9′-Bifluorenylidene

2,2′,7,7′-Tetradiphenylamino-9,9′-bifluorenylidene, TDPABF, was synthesized by reductive dimerization using Lawesson's reagent. It is soluble in common organic solvents such as dichloromethane, chloroform, and 1,2-dichlorobenzene. Its synthesis was confirmed by ¹H-, ¹³C- NMR, MALDI-TOF, and FT-IR spectroscopy. Its HOMO and LUMO energy levels were –5.33 eV and –2.98 eV, respectively, using photoelectron spectroscopy and UV-Vis absorption spectra. Its fluorescence quenching properties were investigated through a Stern-Volmer quenching experiment. The PL intensity significantly decreased on increasing the concentration of TDPABF in a P3HT chloroform solution. The calculated Stern-Volmer quenching constant was 9.1 × 10⁴ M^?1, which is higher than that reported for PC₆₁BM.     

Synthesis of the Copolymer Based on Diketopyrrolopyrrole with Didecyl Chain for OPVs

A new accepter unit, diphenylpyrrolo[3,2-b]pyrrole-2,5-dione with didecyl chain, was prepared and utilized for the synthesis of the conjugated polymer containing electron donor-acceptor pair for OPVs. The iDPP, part of the structure of a natural dye found in lichens, is the regioisomer of the known DPP with switched position of the carbonyl group and nitrogen atom. At the 4-positions of the N-substituted phenyl groups of 1,4-bis(4-butylphenyl)-pyrrolo[3,2-b]-pyrrole-2,5-dione unit in P-butyl, the butyl group was substituted with decyl group to increase solubility. The absorption spectrum of polymer with diphenylpyrrolo[3,2-b]pyrrole-2,5-dione unit exhibit two maximum peaks at about 365 and 542 nm. The spectrum of the P1 as the solid thin film shows absorption band with maximum peaks at 370 and 536 nm, and the absorption onset at 703 nm, corresponding to band gap of 1.76 eV. The oxidation and reduction potential onset of the synthesized polymer were estimated to be 0.84 and ?1.22 V, which correspond to HOMO and LUMO energy levels of ?5.64 and ?3.58 eV, respectively. The devices comprising P1 with PC₆₁BM annealed at 100°C showed a V_OC of 0.79 V, a J_SC of 1.75 mA/cm², and a FF of 0.31, leading to the power conversion efficiency of 0.43% under white light illumination (AM 1.5 G, 100 mW/cm²).     

A novel Zn(II) coordination polymer based on tetra-carboxylates ligand and N-donor ligand: synthesis,structure and photocatalytic properties

Abstract

Novel film polymeric composites based on the non-photoconducting polyvinyl butyral with heterometallic complexes (NH₄)_4n{[Cu(en)(H₂O)][P₂Mo₅O₂₃]}_n·3.5nH₂O (1) and (NH₄)_2n{[Cu(en)₂][Cu(en)(H₂O)][P₂Mo₅O₂₃]}_n·3nH₂O (2) [en?=?ethylenediamine] have been prepared. Both compounds are similar and contain Strandberg anions [P₂Mo₅O₂₃]^6– linked to Cu-diamine species. The main structural difference between complexes is the presence of additional bridging [Cu(en)₂] fragments in 2, which provide an extra connectivity between the neighboring polyoxometalates. However, the different saturations and relaxation times of the photoresponse, as well as different activation energies, are shown. The variability of the photoconducting properties can be explained by the influence of a chain rigidity on the transport of non-equilibrium charge carriers.     

Wide band-gap organic molecules containing benzodithiophene and difluoroquinoxaline derivatives for solar cell applications

Abstract

Two new semiconducting organic small molecules, namely BDTQ-BDT(EH) and BDTQ-BDT(OC), were prepared by attaching electron accepting 2,3-didodecyl-6,7-difluoro-5,8-di(thiophen-2-yl)quinoxaline (DTQ) unit on 2,6-position of electron donating 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene (BDT(EH)) and 4,8-bis(octyloxy)benzo[1,2-b:4,5-b']dithiophene (BDT(OC)) units. Molecule BDTQ-BDT(EH) showed higher thermal stability (5% weight loss temperature, T_d “349 ^оC), slightly lower band-gap (E_g “2.10?eV) and deeper highest occupied molecular orbital energy level (HOMO “–5.36?eV) level compared to those (T_d “336 ^оC, E_g “2.11?eV, and HOMO “–5.30?eV, respectively.) of the molecule BDTQ-BDT(OC). The organic solar cells (OSCs) made with the synthesized molecules as an electron donor and [6,6]-phenyl C₇₁ butyric acid methyl ester (PC₇₀BM) as an electron acceptor gave a maximum power conversion efficiency (PCE) of 1.20% and 0.83%, respectively, for BDTQ-BDT(EH) and BDTQ-BDT(OC). This study confirmed that the substituents attached on the 4,8-position of BDT unit greatly alter the properties of the resulting molecules.     

Single crystals of calcium and strontium phenylphosphonate grown via hydrothermal crystallization

Single crystals of Ca(HO₃PC₆H₅)₂ (1) and Sr(HO₃PC₆H₅)₂ (2) have been obtained via the crystallization of their respective amorphous powders. The amorphous compounds were synthesized by traditional solution routes and were subsequently crystallized at 160°C in a Teflon-lined autoclave containing 1–3 mL distilled water. The resultant single crystals were physically isolated and their structures determined by single crystal X-ray diffraction. The two compounds are isostructural and crystallize in space group C2/c with lattice parameters of a = 31.267(3) ?, b = 5.6185(6) ?, c = 7.7202(8) ?, β = 101.924(2)°; and a = 31.514(4) ?, b = 5.8098(8) ?, c = 7.8218(10) ?, β = 102.063(3)° for the calcium and strontium phenylphosphonate, respectively.     

Fluid Biaxial Banana Smectics: Symmetry at Work

Abstract

Perhaps one of the most surprising results in the past 10 years was the prediction of Brand et al. [1] that fluid biaxial smectics made from comopunds without asymmetric carbons could, by symmetry, have a spontaneous polarization, P, in the layer plane. They called this construct, which can be either ferroelectric or antiferroelectric, smectic C₉. Advances gained from their prediction include the development of highly efficient electrets for broad-band telecommunications [2, 3] as well as a basic non-linear model [4] for TLAFs, thresholdless antiferroelectrics [5], now seen in beatiful, CMOS compatible, active matrix liquid crystal displays [6] (figure 1).     

Crystal structures of three methylmercury(II) complexes with thiazolidine-2-thione

The crystal structures of three CH₃Hg⁺ complexes with 1,3-thiazolidine-2-thione (HT) are reported. The cationic [(CH₃Hg)HT]NO₃ complex is monoclinic, space group P2₁/c,a=7.158(14),b=10.156(7),c=13.472(12) Å,=108.21(4)°,Z=4. The structure was refined toR=0.045. The [(CH₃Hg)HT]⁺ cation contains a CH₃Hg⁺ group bonded to the exocyclic S atom of the ligand retaining its N-H proton. This proton is lost and the CH₃Hg⁺ group remains bonded to sulfur in the neutral [(CH₃Hg)T] compound (hexagonal, P6₃,a=13.502(8),c=6.984(7) Å,Z=6,R=0.027). The [(CH₃Hg)₂T]NO₃ compound (monoclinic, C2/c,a=25.200(10),b=7.029(6),c=17.946(8),=128.99(3)°,Z=8,R=0.047) contains complex cations in which the CH3Hg⁺ groups are bonded to N and the exocyclic S atom. This series of compounds shows that the exocyclic S atom is always the first target for the CH₃Hg⁺ group, which is also found to bind to nitrogen in the 2:1 compound. No coordination is observed with the endocyclic S site, which does not even participate in intermolecular H-bonding or HgS contacts in the solids.     

New sulfur derivatives of 2,3-dichloropyrrolo[1,2-a] benzimidazol-1-one. Demonstration of regioselective thiolate addition and X-ray diffraction structures of 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one

The reaction of thiols with the heterocyclic compound 2,3-dichloropyrrolo[1,2-a] benzimidazol-1-one (1) has been investigated as a route to new redox-active, bidentate sulfur ligands. Treatment of 1 with either methylthiol or benzylthiol in the presence of pyridine affords monosulfide compounds 2-chloro-3-methylthiopyrrolo[1,2-a] benzimidazol-1-one (2) and 2-chloro-3-benzylthiopyrrolo[1,2-a]benzimidazol-1-one (3) and the disulfide derivatives 2,3-di(methylthio)pyrrolo[1,2-a]benzimidazol-1-one (4) and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one (5). The substitution of the first chlorine group in 2,3-dichloropyrrolo[1,2-a]benzimidazol-1-one (1) occurs regioselectively at C-3 to produce 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one (2) and 2-chloro-3-benzylthiopyrrolo[1,2-a]benzimidazol-1-one (3), followed by replacement of the remaining chlorine group to furnish the disulfide compounds 4 and 5. The new thiols have been isolated by column chromatography and characterized in solution by spectroscopic methods. The molecular structures of 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one have been determined by X-ray crystallography. Compound 2 crystallizes as two independent molecules in the monoclinic space group P2₁/c, a = 13.221(2) Å, b = 18.478(2) Å, c = 8.948(1) Å, = 100.088(3)°, V = 2152.3(5) ų, Z = 8, and d_calc = 1.547 Mg/m³; R = 0.0354, R_w = 0.0739 for 2820 reflections with I > 2(I). Compound 5 crystallizes in the triclinic space group P-1, a = 5.180(1) Å, b = 11.494(2) Å, c = 17.243(3) Å, = 86.024(3)°, = 88.606(4)°, = 81.235(3)°, V = 1012.1(4) ų, Z = 2, and d_calc = 1.360 Mg/m³; R = 0.0354, R_w = 0.0692 for 2655 reflections with I > 2(I). The redox properties of the disulfide compounds 4 and 5 have been explored by cyclic voltammetry, where a one-electron reduction at ca. –1.10 V has been observed for each compound. The site of electron accession in has been established by carrying out molecular orbital calculations at the extended Hüuckel level on the model compound 2,3-di(thio)pyrrolo[1,2-a]benzimidazol-1-one.     

Synthesis of quinoxaline-based D-A type conjugated polymers for photovoltaic applications

Abstract

Two quinoxaline-based conjugated polymers were successfully synthesized for application in polymer solar cells (PSCs). The quinoxaline unit with an electron-donating dimethylamino substituent was used as the electron-accepting (A) moiety, whereas indacenodithiophene (IDT) and indacenodithieno-thiophene (IDTT) were chosen as the electron-donating (D) groups to synthesize D-A type conjugated polymers. To investigate the photovoltaic properties of the polymers, an inverted-type device with the configuration of ITO/ZnO/polymer:PC₇₁BM/MoO₃/Ag was fabricated. It has been observed that the overall performances of the organic photovoltaic cells were significantly improved by changing the electron-donating components from IDT to IDTT. Therefore, this study can provide insights into the design and structure–property correlation of quinoxaline-based conjugated polymers for PSCs.     

Enhancement of organic thin-film solar cells by incorporating hybrid Au nanospheres and Au nanorods on a metallic grating surface

Abstract

In this study, we demonstrate the fabrication of hybrid plasmonic solar cells using gold nanoparticles (AuNPs). Two types of AuNPs, gold nanospheres (AuNSs) and gold nanorods (AuNRs), were incorporated in a hole transport layer (HTL) (PEDOT:PSS) on a metallic grating electrode. The organic solar cells (OSCs) structure comprised an indium-tin-oxide (ITO)-coated glass substrate/PEDOT:PSS:AuNSs:AuNRs/P3HT:PCBM/Al grating electrode. Adding AuNPs induced localized surface plasmon resonance (LSPR), while grating structured Al at the interface with a photoactive layer excited the propagating surface plasmons. Compared with a flat reference device, the proposed OSCs exhibited improved photovoltaic properties by increasing both the short-circuit current density (J_SC) and the power conversion efficiency (PCE) with large enhancements of 16.23% and 14.06%, respectively. The efficiency improvement was attributed to increased broadband absorption and improved electrical properties inside the thin-film devices.     

Crystal Structure and Vibrational Spectra of Erbium Trisodium Bis(Cyclotriphosphate) Nonahydrate,ErNa<Subscript>3</Subscript>(P<Subscript>3</Subscript>O<Subscript>9</Subscript>)<Subscript>2</Subscript> · 9H<Subscript>2</Subscript>O

Abstract The cyclotriphosphate salt, ErNa₃(P₃O₉)₂ · 9H₂O, has been characterized by single-crystal X-ray diffraction [hexagonal, space group , with unit cell parameters of a = b = 30.8451(14), c = 12.8063(8) ?; Z = 18]. The structure consists of alternating layers of [P₃O₉]³⁻ groups, ErO₈ dodecahedra, Na(1)O₆ and Na(2)O₇ polyhedra linked together by water molecules. The P₃O₉ rings are grouped along the c-axis in a P₃O₉–ErO₈ arrangement thereby producing broad, hexagonal channels of diameter of 6.65 ? with a side dimension of 3.907 ?. The absence of coincidences for the majority of the IR and Raman bands observed for the cyclotriphosphate salt is in accord with the centrosymmetric structure of the material. The vibrational spectra have been interpreted on the basis of factor group effects. Graphical abstract We report the crystal structure and vibrational spectra of erbium trisodium bis(cyclotriphosphate)nanohydrate salt ErNa ₃ (P ₃ O ₉ ) ₂ · 9H ₂ O H. Assaaoudi, M. Ijjaali, A. Ennaciri, I. S. Butler* and J. A. Kozinski Crystal structure and vibrational spectra of erbium trisodium bis(cyclotriphosphate) nonahydrate,ErNa₃(P₃O₉)₂ · 9H₂O. Projection of the coordination polyhedra of ErNa₃(P₃O₉)₂ · 9H₂O down the c axis     

Emission behavior of naphthalimide-coumarin cassette

ABSTRACT

In this contribution, a dye (C₈-alkyl substituted Naphthalimide-Coumarin, CNC) with naphthalimide and coumarin incorporated together with -NHN = bridge unit. The compound was fully characterized by NMR and HRMS spectroscopic techniques. Highly emissive character was investigated in detail in various polar environments. The emission maximum varied from 430 to 470 nm. In polycarbonate film, CNC is also highly emissive with 560 nm emission peak. While in sold, the emission maximum was further shifted to 580 nm due to the more tightly packing mode than that in film. The C₈-alkyl substitution enhances the solubility of CNC and also contributes most to its solid emission.     

Crystal structure of the molecular inclusion complex of 5, 17-di-t-butyl-26, 28-disubstituted calix[4]arene with acetone (1:3)

Crystal structure of inclusion complex of 5, 17-di-t-butyl-26, 28-disubstituted calix[4]arene 3 with acetone, [(C₅₄H₅₈N₂O₆·CH₃COCH₃)·2CH₃COCH₃], was determined by X-ray crystallographic analysis. It possesses space group C2/c, with a = 26.277(8), b = 12.967(5), c = 20.355(4) Å, = 124.845(14)°, and D _calc = 1.173 mg/m³ for Z = 4. Crystal data indicate that action of one molecule of compound 3 upon three molecules of acetone forms a clathrate intermolecular inclusion complex.     

X-Ray crystal structure determination of a series of 1-aryl- 2-[3-(3-[2-aryl-1-diazenyl]-1,3-diazepan-1-ylmethyl)-1, 3-diazepan-1-yl]-1-diazenes obtained from the reaction of diazonium salts with mixtures of formaldehyde and 1,4-diaminobutane

A new series of bis-triazenes, the 1-aryl-2-[3-(3-[2-aryl-1-diazenyl]-1,3-diazepan-1-ylmethyl)-1,3-diazepan-1-yl]-1-diazenes has been synthesized from the reaction of diazonium salts with a mixture of 1,4-diaminobutane and formaldehyde. The structures of 1-(p-bromophenyl)-2-[3-{3-[2-(p-bromophenyl)-1-diazenyl]-1,3-diazepan-1-ylmethyl}-1,3-diazepan-1-yl]-1-diazene(1), 1-(p-cyanophenyl)-2-[3-{3-[2-(p-cyanophenyl)-1-diazenyl]-1,3-di azepan-1-ylmethyl}-1,3-diazepan-1-yl]-1-diazene(2), and 1-(p-methoxyphenyl)-2-[3-{3-[2-(p-methoxy-phenyl)-1-diazenyl]-1,3-diazepan-1-ylmethyl}-1,3-diazepan-1-yl]-1 diazene(3) have been unequivocally determined by X-ray crystallography. The new bis-triazenes are important since the structure contains the novel saturated heterocycle, 1,3-diazepane. The general conclusion of this study is that alkanediamines with 3 or 4 carbon atoms in the spacer link between the nitrogen atoms give rise to the linear bicyclic molecules of type 5, in contrast to the case of ethylenediamine (spacer link 2 carbon atoms), which affords molecules of type 6, which exemplify the general cage structure of type 4. The crystal structures of 1, 2 and 3 are compared with the previously reported structure of the hexahydropyrimidine analogue 8a(X=CN); compounds 2 and 8a(X=CN) are homologous with respect to the alkane spacer moiety. The structures of 2 and 8a(X=CN) are very different in one respect; in 2 the aryldiazenyl-1,3-diazepanyl groups are in the s-trans orientation around the central methylene group whereas in 8a(X=CN) the arrangement of the aryldiazenyl-hexahydropyrimidinyl groups is the s-cis orientation.Crystal data: 1 C₂₃H₃₀N₈Br₂, triclinic, space group P-1, a=8.3979(2), b=10.7828(3), c=14.4692(5) ?, α=83.670(1), β=78.662(1), γ=78.758(1)°, V=1256.48(6) ?³, for Z=2. 2 C₂₅H₃₀N₁₀, monoclinic, space group P2 ₁ /n, a=13.4046(6), b=9.4482(4), c=10.6913(4)?, β=103.239(2)°, V=2490.5(2) ?³, for Z=4. 3 C₂₅H₃₆N₈O₂, triclinic, space group P-1, a=8.5223(3), b=10.6913(4), c=14.4034(7)?, α=85.657(2), β=78.731(2), γ=80.153(1)°, V=1266.88(9) ?³, for Z=2.