Donor Materials For Organic Solar Cells Research Articles

A Multifluorination Strategy Toward Wide Bandgap Polymers for Highly Efficient Organic Solar Cells

AbstractCreating new electron‐deficient unit is highly demanded to develop high‐performance polymer donors for non‐fullerene organic solar cells (OSCs). Herein, we reported a multifluorinated unit 4,5,6,7‐tetrafluoronaphtho[2,1‐b : 3,4‐b′]dithio‐phene (FNT) and its polymers PFNT‐F and PFNT‐Cl. The advantages of multifluorination: (1) it enables the polymers to exhibit low‐lying HOMO (≈−5.5 eV) and wide band gap (≈2.0 eV); (2) the short interactions (F⋅⋅⋅H, F⋅⋅⋅F) endow the polymers with properties of high film crystallinity and efficient hole transport; (3) well miscibility with NFAs that leads to a more well‐defined nanofibrous morphology and face‐on orientation in the blend films. Therefore, the PFNT‐F/Cl : N3 based OSCs exhibit impressive FF values of 0.80, and remarkable PCEs of 17.53 % and 18.10 %, which make them ranked the best donor materials in OSCs. This work offers new insights into the rational design of high‐performance polymers by multifluorination strategy.

A Multifluorination Strategy Toward Wide Bandgap Polymers for Highly Efficient Organic Solar Cells.

Creating new electron-deficient unit is highly demanded to develop high-performance polymer donors for non-fullerene organic solar cells (OSCs). Herein, we reported a multifluorinated unit 4,5,6,7-tetrafluoronaphtho[2,1-b : 3,4-b']dithio-phene (FNT) and its polymers PFNT-F and PFNT-Cl. The advantages of multifluorination: (1) it enables the polymers to exhibit low-lying HOMO (≈-5.5 eV) and wide band gap (≈2.0 eV); (2) the short interactions (F⋅⋅⋅H, F⋅⋅⋅F) endow the polymers with properties of high film crystallinity and efficient hole transport; (3) well miscibility with NFAs that leads to a more well-defined nanofibrous morphology and face-on orientation in the blend films. Therefore, the PFNT-F/Cl : N3 based OSCs exhibit impressive FF values of 0.80, and remarkable PCEs of 17.53 % and 18.10 %, which make them ranked the best donor materials in OSCs. This work offers new insights into the rational design of high-performance polymers by multifluorination strategy.

Structural, Electronic, and Charge Transport Properties of New Materials based on 2-(5-Mercapto-1,3,4-Oxadiazol-2-yl) Phenol for Organic Solar Cells and Light Emitting Diodes by DFT and TD-DFT

This work reports on the density functional theory (DFT) and its time-dependent extension (TD-DFT) study of the structural, electronic, and charge transport properties of 2-(5-mercapto-1,3,4-oxadiazol-2-yl) phenol (MODP) and some of its transition M2+ complexes (M = Fe, Co, Cu, Ni, Zn, Pd, Pt). Reorganization energy, integral charge transfer, mobility, open circuit voltage, and electronic properties of these compounds have been calculated by employing the global hybrid functional PBE0 in conjunction with the Karlsruhe basis set def2-TZVP. Results show that MODP and its transition metal complexes are good electron donors for organic solar cells (OSC) owing to their relatively higher HOMO and LUMO energies compared to the prototypical (6, 6)-phenyl-C61-butyric acid methyl ester (PCBM). Energy gaps ranging between 2.502 and 4.455 eV, energy driving forces (∆EL-L) ranging between 2.08 and 2.44 eV, and large open circuit voltages ( V OC ) ranging from 1.12 to 2.05 eV were obtained. The results also revealed that MODP and its Pd(II) and Pt(II) complexes could serve as ambipolar charge transport materials owing to their very small reorganization energies, integral charge transfers, high rate charge transfers, and mobilities. All studied molecules showed OSC donor and hole/electron transport characteristics required by organic light-emitting diodes (OLEDs). Based on these results, new ways for designing charge transport materials for OLEDs as well as donor materials in OSCs are proposed.

Low Cost Synthesis and Characterization of Donor P3HT Polymer for Fabrication of Organic Solar Cell

Over the years, the conjugated polymers acts as electron donor material in the active layer of Organic solar cells (OSCs). By altering means of doping, prepare a composite with suitable materials from Poly (p-phenylene vinylene) PPV polymer toPM6 polymer which gives Power conversion efficiency (PCE) can vary from ~ 2% to ~15%. But these are expensive, complicated synthetic procedure and less availability. To overcome this,the conjugated polymer Poly (3-Hexyl Thiophene)(P3HT) synthesized through oxidative coupling of 3-HT monomer and Ferric chloride (FeCl3) as an oxidant which is low cost, available and very easy method of synthesis. We investigated synthesized P3HT material that shows the Fourier Transform Infrared(FTIR) peaks shows that intramolecular interactions from thiophene ring, alkyl chain and polymer chain, FESEM Images reveals morphology consists of condensed layers in micrometer dimensions and Cyclic voltammetry studies gives oxidation and reduction potentials to promote the higher ionization potential of the compound to use as donor material in OSCs.

Computational study on optoelectronic and charge transport properties of diketopyrrolopyrrole-based A-D-A-D-A structure molecules for organic solar cells.

Eight novel diketopyrrolopyrrole (DPP)-based A-D-A-D-A structure molecules were designed for organic solar cells (OSCs) applications. In these molecules, the electron-deficient DPP and dicyanovinyl groups were used as the acceptor groups and different planar electron-rich groups were employed as the donor π-bridges. Applying the B3LYP/6-31G (d,p) and TD-B3LYP/6-31G (d,p) methods, the optoelectronic and charge transport properties were investigated. It turned out that the different π-bridges can tune effectively the frontier molecular orbital energy levels, band gap, and absorption spectra. Furthermore, the different π-bridges also affect the charge transport properties of the designed molecules. Our results suggest that the investigated molecules can serve as donor materials. Additionally, some investigated molecules can also be used as hole and/or electron transport materials for OSCs. Graphical abstract A series of novel A-D-A-D-A molecules are investigated systematically. The optical and electronic properties can be tuned effectively by the π-bridges. All derivatives can be used as donor materials for OSCs. Some designed molecules can be used as hole and/or electron transport materials. The different π-bridges do not significantly affect the stability of the molecules.

A New Small-Molecule Donor Containing Non-Fused Ring π-Bridge Enables Efficient Organic Solar Cells with High Open Circuit Voltage and Low Acceptor Content.

To achieve high open-circuit voltage (Voc ) and low acceptor content, the molecular design of a small-molecule donor with low energy loss (Eloss ) is very important for solution-processable organic solar cells (OSCs). Herein, we designed and synthesized a new coplanar A-D-A structured organic small-molecule semiconductor with non-fused ring structure π-bridge, namely B2TPR, and applied it as donor material in OSCs. Owing to the strong electron-withdrawing effect of the end group and the coplanar π-bridge, B2TPR exhibits a low-lying highest occupied molecular orbital and strong crystallinity. Furthermore, benefiting from the coplanar molecular skeleton, the high hole mobility, balanced charge transport and reduced recombination were achieved, leading to a high fill factor (FF). The OSCs based on B2TPR : PC71 BM blend film (w/w=1 : 0.35) demonstrates a moderate power conversion efficiency (PCE) of 7.10 % with a remarkable Voc of 0.98 V and FF of 64 %, corresponding to a low fullerene content of 25.9 % and a low Eloss of 0.70 eV. These results demonstrate the great potential of small-molecule with structure of B2TPR for future low-cost organic photovoltaic applications.

Rational design of diketopyrrolopyrrole-based multifunctional materials for organic light-emitting diodes and organic solar cells

A series of donor–acceptor diketopyrrolopyrrole derivatives has been investigated to reveal their optical, electronic, and charge transport properties for applications in organic light-emitting diodes (OLEDs) and organic solar cells (OSCs). The calculated results show that their optical, electronic, and charge transport properties are affected by the different end groups. The introduction of the 2,5-diphenylthiophene, benzo[c]isothiazole, benzo[c]thiophene, benzo[c]thiophene, 2,4-dihydrobenzo[d]thiazole, and thieno[3,4-b][1,4] dioxine end groups can broaden absorption spectrum and improve charge transport property of the designed compounds. Our results suggest that the designed compounds can serve as donor materials for OSCs and luminescent materials for OLEDs. In addition, the mobility of the designed compounds is also investigated. They are expected to be promising candidates for hole and electron transport materials. On the basis of investigated results, we proposed a rational way for the design of multifunctional materials for OLED and OSC applications.

Rational design of multifunctional star-shaped molecules with a 1,3,5-triazine core and different arms for application in organic light-emitting diodes and organic solar cells.

A series of star-shaped 1,3,5-triazine derivatives for intended application in organic light-emitting diodes (OLEDs) and organic solar cells (OSCs) were investigated theoretically to explore their optical, electronic, and charge-transport properties. Analysis of their frontier molecular orbitals (FMOs) indicated that vertical electronic transitions associated with absorption and emission by these derivatives can be characterized as intramolecular charge-transfer (ICT) processes. The calculated results show that the optical, electronic, and charge-transport properties of the derivatives are influenced by the end groups and π-bridges present. Our results suggest that the molecules under investigation could serve as donor materials in OSCs and/or luminescent materials in OLEDs. In addition, all of the molecules are expected to be promising candidates for hole- and electron-transport materials. Based on our results, we were able to propose a rational method of designing multifunctional materials for application in OLEDs and OSCs. Graphical abstract A series of multifunctional star-shaped small molecules were investigated as charge-transport and luminescent materials for OLEDs as well as charge-transport and donor materials for OSCs.

Triphenylamine-containing linear D-A-D molecules with benzothiadiazole as acceptor unit for bulk-heterojunction organic solar cells

Three solution-processable triphenylamine (TPA)-containing low band gap D-A-D molecules with benzothiadiazole (BT) as acceptor unit and TPA-(4-hexyl)thiophene (TPA-HT), TPA-(4-hexyl)thieno[3,2-b]thiophene (TPA-HTT) and bis(octyloxy)TPA-(4-hexyl)thieno[3,2-b]thiophene (boTPA-HTT) as donor units, TPA-HT-BT, TPA-HTT-BT and boTPA-HTT-BT, have been designed and synthesized for the application in the bulk-heterojunction organic solar cells (OSCs). The molecules show broad absorption band in the visible range and appropriate HOMO energy levels for the donor materials in OSCs. The OSC devices were fabricated with the molecules as donor and PC 70BM as acceptor. The power conversion efficiencies of the OSCs based on TPA-HT-BT, TPA-HTT-BT and boTPA-HTT-BT reached 1.44%, 1.44% and 0.75%, respectively, under the illumination of AM.1.5, 100 mW/cm 2.

Naphtho[2,3,a]pyrene as an efficient multifunctional organic semiconductor for organic solar cells, organic light-emitting diodes, and organic thin-film transistors

Abstract We found that naphtho[2,3,a]pyrene (NP) can be commonly used as an effective tri-functional material for three representative kinds of devices in organic electronics. In order to prove the fact, we fabricated organic solar cells (OSCs), organic light-emitting diodes (OLEDs), and organic thin-film transistors (OTFTs) using NP as their active layer. First, an optimized 80 nm-thick NP based OSC device exhibited a good power conversion efficiency of 0.48% in OSCs. Second, OLEDs with 3% NP doping showed sky blue emission and a power efficiency of 3.4 lm W−1 and a current efficiency of 4.4 cd A−1. OLEDs with 5% NP doping showed green emission and a power efficiency of 1.8 lm W−1 and a current efficiency of 3.9 cd A−1. Third, OTFTs based on NP exhibited a field-effect mobility (μFET) of 0.12 cm2 V−1 s−1, a threshold voltage (Vth) of −10.8 V, and an on/off ratio of 6.8 × 106. These results indicated that NP can be efficiently used as a donor material in OSCs, a blue and green emitting material in OLEDs, and a charge transport channel in OTFTs.