Synthesis and characterization of a series of low-bandgap copolymers based on cyclopenta[2,1-b:3,4-b′]dithiophene and thienopyrroledione for photovoltaic applications

Hong, Young-Rae; Ng, Joo Yee; Wong, Hoi Ka; Moh, Lionel C. H.; Yip, Yong Jie; Chen, Zhi-Kuan; Norsten, Tyler B.

doi:10.1016/j.solmat.2012.03.028

Cited by 10 publications

(5 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An effective strategy in polymer donor design involves employing a conjugated framework with multiple fused rings where a ladder-type building block forces the backbone into planarity, extends the conjugation length, improves electron delocalization, reduces rotational disorder, and enhances physical, chemical, and mechanical stabilities of the polymers . Common multiple-ring electron-rich moieties include benzodithiophene (BDT), − dithienosilole (DTS), − dithienogermole (DTG), − and cyclopentadithiophene − (CPDT, also called DTC in this paper to be consistent with acronyms DTS and DTG). In the case of electron-deficient moieties, thienopyrrolodione (TPD), − isoindigo (iI), − diketopyrrolopyrrole (DPP), , and benzothiadiazole (BTD) − all consist of fused structures.…”

Section: Introductionmentioning

confidence: 99%

Every Atom Counts: Elucidating the Fundamental Impact of Structural Change in Conjugated Polymers for Organic Photovoltaics

Gautam

Selter

et al. 2018

Chem. Mater.

View full text Add to dashboard Cite

As many conjugated polymer-based organic photovoltaic (OPV) materials provide substantial solar power conversion efficiencies (as high as 13%), it is important to develop a deeper understanding of how the primary repeat unit structures impact device performance. In this work, we have varied the group 14 atom (C, Si, Ge) at the center of a bithiophene fused ring to elucidate the impact of a minimal repeat unit structure change on the optical, transport, and morphological properties, which ultimately control device performance. Careful polymerization and polymer purification produced three "one-atom change" donor−acceptor conjugated alternating copolymers with similar molecular weights and dispersities. DFT calculation, absorption spectroscopy, and high-temperature solution 1 H nuclear magnetic resonance (NMR) results indicate that poly(dithienosilole-alt-thienopyrrolodione), P(DTS-TPD), and poly-(dithienogermole-alt-thienopyrrolodione), P(DTG-TPD) exhibit different rotational conformations when compared to poly(cyclopentadithiophene-alt-thienopyrrolodione), P(DTC-TPD). Solid-state 1 H MAS NMR experiments reveal that the greater probability of the anticonformation in P(DTS-TPD) and P(DTG-TPD) prevail in the solid phase. The conformational variation seen in solution and solid-state NMR in turn affects the polymer stacking and intermolecular interaction. Twodimension 1 H-1 H DQ-SQ NMR correlation spectra shows aromatic−aromatic correlations for P(DTS-TPD) and P(DTG-TPD), which on the other hand is absent for P(DTC-TPD). In a thin-film interchain packing study using grazing incidence wide-angle X-ray scattering (GIWAXS), we observe the π-face of the conjugated backbones of P(DTC-TPD) aligned edge-on to the substrate, whereas in contrast the π-faces of P(DTS-TPD) and P(DTG-TPD) align parallel to the surface. These differences in polymer conformations and backbone orientations lead to variations in the OPV performance of blends with the fullerene PC 71 BM, with the device containing P(DTC-TPD):PCBM having a lower fill factor and a lower power conversion efficiency. Ultrafast transient absorption spectroscopy shows the P(DTC-TPD):PCBM blend to have a more pronounced triplet formation from bimolecular recombination of initially separated charges. With a combination of sub-bandgap external quantum efficiency measurements and DFT calculations, we present evidence that the greater charge recombination loss is the result of a lower lying triplet energy level for P(DTC-TPD), leading to a higher rate of recombination and lower OPV device performance. Importantly, this study ties ultimate photovoltaic performance to morphological features in the active films that are induced from the processing solution and are a result of minimal one-atom differences in polymer repeat unit structure.

show abstract

Section: Introductionmentioning

confidence: 99%

Every Atom Counts: Elucidating the Fundamental Impact of Structural Change in Conjugated Polymers for Organic Photovoltaics

Gautam

Selter

et al. 2018

Chem. Mater.

View full text Add to dashboard Cite

show abstract

“…The ability to control the chemical structure of conjugated polymers is critically important to determine their properties and optimize the performance of PSCs. Even small modifications can induce dramatic effects on the physical and chemical properties of conjugated polymers, including their solubility, crystallinity, interchain packing, light absorption, and electrochemical properties. − In this regard, the effects of the structural modifications in the alkyl solubilizing groups and the polymer backbone on the properties of conjugated polymers have been widely investigated. − In particular, the introduction of an additional atom into the polymer backbone provides a promising pathway to fine-tune the electrochemical and physical properties of conjugated polymers, and this approach generally causes dramatic changes in the photovoltaic performance of the polymers. , For example, Yu and co-workers have reported that the introduction of fluorine atoms into a polymer backbone lowered both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels, which induced changes in the polymer’s electrochemical properties and significantly increased the PCE of PSCs from 2.3% to 7.2% . In addition to fluorination, other research groups have reported the effects of introduced oxygen atoms on the properties and the photovoltaic performance of polymers. − …”

Section: Introductionmentioning

confidence: 99%

Effect of Incorporated Nitrogens on the Planarity and Photovoltaic Performance of Donor–Acceptor Copolymers

et al. 2012

View full text Add to dashboard Cite

Systematic control of the chemical structure of conjugated polymers is critically important to elucidate the relationship between the conjugated polymer structures and properties and to optimize their performance in bulk heterojunction (BHJ) polymer solar cell (PSC) devices. Herein, we synthesized three new copolymers, i.e., P0, P1, and P2; these copolymers contain the same benzodithiophene donor unit but have different acceptor units with different numbers of nitrogen atoms in the range of 0–2. The effects of the introduced nitrogen atoms on the structural, optical, electrical, and photovoltaic properties of the conjugated polymers were investigated; the structural properties of the polymers, in particular, were studied using both experimental (grazing-incidence X-ray scattering (GIXS) measurements) and computational methods (molecular simulation). As the number of introduced nitrogen atoms increased, the planarity of the main chain conformation increased in the order of P0 < P1 < P2. Additionally, the P0, P1, and P2 polymers showed increased interlayer domain spacings of 1.61, 1.72, and 1.78 nm, respectively, with increased intermolecular ordering. These results were in excellent agreement with the simulation results. In addition, the enhanced planarity resulted in a red-shifting at the onset of absorption in the polymer film from 544 to 585 nm, a downshift in the lowest unoccupied molecular orbital (LUMO) energy level from −3.02 to −3.26 eV, and an increase in the hole mobility from 2.33 × 10–6 to 3.78 × 10–5 cm2/(V s). As a result, we observed dramatically enhanced performance of the PSCs in the order of P0 < P1 < P2. For example, the P2:PC61BM device exhibited a 3.5-fold improvement in power conversion efficiency (PCE) compared to that of P0:PC61BM. The further optimization of P2 with PC71BM showed the PCE of 3.22%.

show abstract

“…By incorporating fused ring aromatic moieties, the polymer coplanarity can be extended facilitating intermolecular packing, and thus, charge carrier transport can be improved. Besides cyclopentanedithiophene and naphthodithiophene, thienothiophene was proven to be a good building block for high charge carrier mobilities. − TPD copolymers containing thienothiophene show high performance as a donor material in organic solar cells and in p-type OFETs. In detail, a solar cell efficiency of 9.21% in combination with a fullerene-based acceptor and an OFET hole mobility of 1.29 cm 2 V –1 s –1 was achieved, which are both the highest values for TPD copolymers reported to date.…”

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Highly Efficient and Balanced Charge Transport in Thieno[3,4-c]pyrrole-4,6-dione Copolymers: Dramatic Influence of Thieno[3,2-b]thiophene Comonomer on Alignment and Charge Transport

et al. 2018

View full text Add to dashboard Cite

The design, synthesis, characterization, and application of a novel series of copolymers based on the electron deficient thieno [3,4-c]pyrrole-4,6-dione building block, copolymerized with either thieno[3,2-b]thiophene (PTPDTT) or thiophene (PTPDT), are reported. High molecular weights were obtained for PTPDTT via Stille polycondensation. For the PTPDTs, different molecular weights were achieved by varying the polymerization conditions. The increase in molecular weight (PTPDT-2) favors face-on alignment and increases the charge carrier mobility. Grazing-incidence wideangle X-ray scattering measurements reveal higher crystallinity for PTPDTT with up to 5 orders of lamellar stacking compared to PTPDTs. All polymers show ambipolar charge transport with highly balanced hole and electron mobilities in organic field effect transistors (OFETs), which improve considerably upon thermal annealing. A shift of comonomer from simple thiophene in PTPDT-2 to planar and electron-dense thienothiophene in PTPDTT drastically changes the alignment from face-on to edge-on fashion. Consequently, the charge carrier mobility increases considerably by 1 order of magnitude in PTPDTT, reaching excellent charge carrier mobilities for both holes (0.11 cm 2 V −1 s −1 ) and electrons (0.17 cm 2 V −1 s −1 ). PTPDTT was tested as a donor material in combination with PC 71 BM as well as an acceptor material along with a donor polymer. As a donor material, a power conversion efficiency of 4.3% was reached in combination with PC 71 BM.

show abstract

Synthesis and characterization of a series of low-bandgap copolymers based on cyclopenta[2,1-b:3,4-b′]dithiophene and thienopyrroledione for photovoltaic applications

Cited by 10 publications

References 49 publications

Every Atom Counts: Elucidating the Fundamental Impact of Structural Change in Conjugated Polymers for Organic Photovoltaics

Every Atom Counts: Elucidating the Fundamental Impact of Structural Change in Conjugated Polymers for Organic Photovoltaics

Effect of Incorporated Nitrogens on the Planarity and Photovoltaic Performance of Donor–Acceptor Copolymers

Highly Efficient and Balanced Charge Transport in Thieno[3,4-c]pyrrole-4,6-dione Copolymers: Dramatic Influence of Thieno[3,2-b]thiophene Comonomer on Alignment and Charge Transport

Contact Info

Product

Resources

About