Identifying the origin of delayed electroluminescence in a polariton organic light-emitting diode

Modifying the energy landscape of existing molecular emitters is an attractive challenge with favourable outcomes in chemistry and organic optoelectronic research. It has recently been explored through strong light-matter coupling studies where the organic emitters were placed in an optical cavity. Nonetheless, a debate revolves around whether the observed change in the material properties represents novel coupled system dynamics or the unmasking of pre-existing material properties induced by light-matter interactions. Here, for the first time, we examined the effect of strong coupling in polariton organic light-emitting diodes via time-resolved electroluminescence studies. We accompanied our experimental analysis with theoretical fits using a model of coupled rate equations accounting for all major mechanisms that can result in delayed electroluminescence in organic emitters. We found that in our devices the delayed electroluminescence was dominated by emission from trapped charges and this mechanism remained unmodified in the presence of strong coupling.Comment: 11 pages + 8 supp pages, 4 figures + 8 supp figure

Chargeâ Transport Properties of F6TNAPâ Based Chargeâ Transfer Cocrystals

The crystal structures of the chargeâ transfer (CT) cocrystals formed by the Ï â electron acceptor 1,3,4,5,7,8â hexafluoroâ 11,11,12,12â tetracyanonaphthoâ 2,6â quinodimethane (F6TNAP) with the planar Ï â electronâ donor molecules triphenylene (TP), benzo[b]benzo[4,5]thieno[2,3â d]thiophene (BTBT), benzo[1,2â b:4,5â bâ ²]dithiophene (BDT), pyrene (PY), anthracene (ANT), and carbazole (CBZ) have been determined using singleâ crystal Xâ ray diffraction (SCXRD), along with those of two polymorphs of F6TNAP. All six cocrystals exhibit 1:1 donor/acceptor stoichiometry and adopt mixedâ stacking motifs. Cocrystals based on BTBT and CBZ Ï â electron donor molecules exhibit brickwork packing, while the other four CT cocrystals show herringboneâ type crystal packing. Infrared spectroscopy, molecular geometries determined by SCXRD, and electronic structure calculations indicate that the extent of groundâ state CT in each cocrystal is small. Density functional theory calculations predict large conduction bandwidths and, consequently, low effective masses for electrons for all six CT cocrystals, while the TPâ , BDTâ , and PYâ based cocrystals are also predicted to have large valence bandwidths and low effective masses for holes. Chargeâ carrier mobility values are obtained from spaceâ charge limited current (SCLC) measurements and fieldâ effect transistor measurements, with values exceeding 1 cm2 Vâ 1 s1 being estimated from SCLC measurements for BTBT:F6TNAP and CBZ:F6TNAP cocrystals.Structural, electronic band structure, and electrical properties of a series of chargeâ transfer cocrystals based on F6TNAP and six planar donors are presented. Density functional theory calculations afford large conduction bandwidths and low effective masses for all six cocrystals. A few cocrystals exhibit chargeâ carrier mobilities in excess of 1 cm2 Vâ 1 sâ 1, as estimated from spaceâ charge limited current measurements.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153248/1/adfm201904858-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153248/2/adfm201904858.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153248/3/adfm201904858_am.pd

Geometric, electronic and optical properties of organic charge transfer systems: Photovoltaic blends and donor-acceptor co-crystals

Over the past two decades, π-conjugated organic molecules have found applications in the active layer of different types of organic electronic devices. To optimize and improve the performance of each of these devices, it is important to establish clear connections between chemical-structure, intermolecular packing and their impact on the electronic and charge transport properties in these systems. In this Thesis, we focus on two-component organic material systems – one acting as a π-electron donor (D) and the other as a π-electron acceptor (A) for applications in organic photovoltaics (OPV) and organic field-effect transistors (OFETs). On the OPV side (Chapters 3 & 4), initially, we investigate the solution temperature-dependent aggregation property of a few polymers in their pure phases, which has been recently established as a potential method for morphology control in high-performing OSC devices. We then explore the intermolecular packing properties in the binary blends of polymer and two small molecule acceptors, which in their binary as well as ternary combinations exhibit high power conversion efficiencies. We elucidate clear connections between the molecular scale features that impact the device parameters in both the binary blends. We also obtain useful trends to explain the linear evolution of device parameters in the ternary blends. On the OFET side (Chapters 5 & 6), our focus is on DA charge-transfer co-crystals, which possess potential applications as active layer components in OFET devices. Initially, we investigate the effect of packing on electronic properties of co-crystals based on F6TNAP acceptor and a series of donor molecules. Further, we focus on understanding the evolution in electronic, vibrational and charge-transport properties with sequential addition of alkyl chains on the donor and fluorine atoms on the acceptor on co-crystals based on BTBT-FmTCNQ (m=0, 2, 4) and di-CnBTBT-FmTCNQ (n=8, 12; m=0, 4) series. Finally, we explore the degree of charge-transfer in these systems using an approach based on Mulliken charges. While these results are limited to the systems under consideration, our simulations provide a reliable, molecular-level understanding to systematically improve the morphological characteristics that impact the device performances in organic electronic devices.Ph.D

Describing terminologies and discussing records: More discoveries of facultative vivipary in the genus Hedychium J.Koenig (Zingiberaceae) from Northeast India

Volume: 96Start Page: 21End Page: 3

Hedychium ziroense (Zingiberaceae), a new species of ginger lily from Northeast India

We describe Hedychium ziroense sp. nov. from Northeast India (NE India) which was discovered during one of our recent botanical explorations in Arunachal Pradesh. We provide detailed morphological comparison of this species with four other Hedychium species (H. griersonianum R.M.Sm., H. ellipticum Buch.-Ham. ex Sm., H. gomezianum Wall. and H. yunnanense Gagnep.), with which it shares some morphological similarities. The new species is characterised by a dense cylindrical spike, pubescent rachis, folded bracts, 2–3 flowers per cincinnus, deeply cleft labellum and a distinctive late monsoonal flowering phenology from August to September

Mangrove Palm – A Versatile Unique Palm

53-54Palms are valued because of their beauty and economic value

Bulk Heterojunction Solar Cells: Insight into Ternary Blends from a Characterization of the Intermolecular Packing and Electronic Properties in the Corresponding Binary Blends

While adding a third component to a binary blend in the active layer of an organic solar cell is a promising approach to improve device performance, the control of active-layer morphology also becomes more complex. Here, a combination of molecular dynamics simulations and long-range corrected density functional theory calculations is used to examine the intermolecular packing and electronic properties in two polymer donor/small-molecule acceptor binary blends, D/A1 (donor/acceptor1) and D/A2 (donor/acceptor2), in order to gain insight into the D/A1/A2 ternary blend. The focus is on the blends of the 4-(3-(2-decyltetradecyl)-5 '-(2,3-difluoro-4-(5-methylthiophen-2-yl)phenyl)-[2,2 '-bithiophen]-5-yl)-7-(4-(2-decyltetradecyl)-5-methylthiophen-2-yl)-5,6-difluoro-2-propyl-2H-benzo[d][1,2,3]triazole (PTFB-O) polymer donor with the 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(5-hexylthienyl)-dithieno[2,3-d:2 ',3 '-d ']-s-indaceno[1,2-b:5,6-b ']dithiophene (ITIC-Th) and 2,2 '-((2Z,2 ' Z)-(((4,4,9,9-tetrakis(5-hexylthiophen-2-yl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b ']dithiophene-2,7-diyl)bis(4-octylthiophene-5,2-diyl))-bis(methanylylidene))bis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))-dimalononitrile (IEIC-Th) acceptors. The intermolecular packings and extent of mixing between the polymer donor and the acceptor in both binary blends are found to be similar, which is consistent with the well-mixed nature of the ITIC-Th:IEIC-Th phase and the quasi-linear evolution of open-circuit voltage as a function of ITIC-Th concentration in the PTFB-O:ITIC-Th:IEIC-Th ternary blend. The intermolecular packing patterns and electron-transfer rates among the acceptors are explored to rationalize the higher electron mobility found in the PTFB-O:ITIC-Th blend. The energetic distribution of the charge-transfer electronic states and non-radiative recombination rates are also evaluated to understand the difference in voltage losses between the binary blends.12 month embargo; published online: 8 June 2020This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Bulk Heterojunction Solar Cells: Insight into Ternary Blends from a Characterization of the Intermolecular Packing and Electronic Properties in the Corresponding Binary Blends

While adding a third component to a binary blend in the active layer of an organic solar cell is a promising approach to improve device performance, the control of active-layer morphology also becomes more complex. Here, a combination of molecular dynamics simulations and long-range corrected density functional theory calculations is used to examine the intermolecular packing and electronic properties in two polymer donor/small-molecule acceptor binary blends, D/A1 (donor/acceptor1) and D/A2 (donor/acceptor2), in order to gain insight into the D/A1/A2 ternary blend. The focus is on the blends of the 4-(3-(2-decyltetradecyl)-5 '-(2,3-difluoro-4-(5-methylthiophen-2-yl)phenyl)-[2,2 '-bithiophen]-5-yl)-7-(4-(2-decyltetradecyl)-5-methylthiophen-2-yl)-5,6-difluoro-2-propyl-2H-benzo[d][1,2,3]triazole (PTFB-O) polymer donor with the 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(5-hexylthienyl)-dithieno[2,3-d:2 ',3 '-d ']-s-indaceno[1,2-b:5,6-b ']dithiophene (ITIC-Th) and 2,2 '-((2Z,2 ' Z)-(((4,4,9,9-tetrakis(5-hexylthiophen-2-yl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b ']dithiophene-2,7-diyl)bis(4-octylthiophene-5,2-diyl))-bis(methanylylidene))bis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))-dimalononitrile (IEIC-Th) acceptors. The intermolecular packings and extent of mixing between the polymer donor and the acceptor in both binary blends are found to be similar, which is consistent with the well-mixed nature of the ITIC-Th:IEIC-Th phase and the quasi-linear evolution of open-circuit voltage as a function of ITIC-Th concentration in the PTFB-O:ITIC-Th:IEIC-Th ternary blend. The intermolecular packing patterns and electron-transfer rates among the acceptors are explored to rationalize the higher electron mobility found in the PTFB-O:ITIC-Th blend. The energetic distribution of the charge-transfer electronic states and non-radiative recombination rates are also evaluated to understand the difference in voltage losses between the binary blends.12 month embargo; published online: 8 June 2020This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Charge‐Transport Properties of F 6

The crystal structures of the chargeâ transfer (CT) cocrystals formed by the Ï â electron acceptor 1,3,4,5,7,8â hexafluoroâ 11,11,12,12â tetracyanonaphthoâ 2,6â quinodimethane (F6TNAP) with the planar Ï â electronâ donor molecules triphenylene (TP), benzo[b]benzo[4,5]thieno[2,3â d]thiophene (BTBT), benzo[1,2â b:4,5â bâ ²]dithiophene (BDT), pyrene (PY), anthracene (ANT), and carbazole (CBZ) have been determined using singleâ crystal Xâ ray diffraction (SCXRD), along with those of two polymorphs of F6TNAP. All six cocrystals exhibit 1:1 donor/acceptor stoichiometry and adopt mixedâ stacking motifs. Cocrystals based on BTBT and CBZ Ï â electron donor molecules exhibit brickwork packing, while the other four CT cocrystals show herringboneâ type crystal packing. Infrared spectroscopy, molecular geometries determined by SCXRD, and electronic structure calculations indicate that the extent of groundâ state CT in each cocrystal is small. Density functional theory calculations predict large conduction bandwidths and, consequently, low effective masses for electrons for all six CT cocrystals, while the TPâ , BDTâ , and PYâ based cocrystals are also predicted to have large valence bandwidths and low effective masses for holes. Chargeâ carrier mobility values are obtained from spaceâ charge limited current (SCLC) measurements and fieldâ effect transistor measurements, with values exceeding 1 cm2 Vâ 1 s1 being estimated from SCLC measurements for BTBT:F6TNAP and CBZ:F6TNAP cocrystals.Structural, electronic band structure, and electrical properties of a series of chargeâ transfer cocrystals based on F6TNAP and six planar donors are presented. Density functional theory calculations afford large conduction bandwidths and low effective masses for all six cocrystals. A few cocrystals exhibit chargeâ carrier mobilities in excess of 1 cm2 Vâ 1 sâ 1, as estimated from spaceâ charge limited current measurements.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153248/1/adfm201904858-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153248/2/adfm201904858.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153248/3/adfm201904858_am.pd