Browsing by Author "Golder, Jan"

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Anode interlayer in organic photovoltaics: Narrow bandgap small molecular materials as exciton-blocking layer
(2019-11-01)
Golder, Jan
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Lin, Chiao-Wen
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Chen, Chin-Ti
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應用化學系
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Department of Applied Chemistry
Six materials were used as an interlayer at the anode side (anode interlayer [AIL]) of an archetypical planar heterojunction organic solar cell (OSC). In addition to two conventional wide bandgap hole transport materials (HTMs), tris(4-carbazol-9-ylphenyl)amine (TCTA) and trans-4,4 '-bis[N-(naphthalen-1-yl)-N-phenylamino]stilbene (NPAE), we explore four narrow bandgap materials, bis(biphenylaminospiro)-fumaronitrile (PhSPFN), bis(N-(naphthalen-1-yl)-N-phenylamino)anthraquinone (NPAAnQ), bis-(di(2-fluorophenyl)aminospiro)-fumaronitrile (FPhSPFN), and bis[4-(N-(pyren-1-yl)-N-phenylamino)phenyl]fumaronitrile (PyPAFN), the energy levels of which essentially align with the ones of SubPc, the active light-absorbing material of the OSC study herein. By using a narrow bandgap AIL, universally enhanced short-circuit current density and power conversion efficiencies (PCEs) have been achieved. In addition, one of these materials, FPhSPFN, results in a PCE of 5.13%, which is the highest reported value for SubPc solar cells with a similar architecture. This is ascribed to the formation of an otherwise passive exciton-blocking interface. Furthermore, this demonstrates that charge selectivity by way of a high-lying lowest unoccupied molecular orbital (LUMO) energy level is not a prerequisite for successful AIL design. As such, in terms of energy level alignment and bandgap energies, we establish a viable alternative approach toward interface and interlayer material design.
Oligothiophenes and alkyl side-chain arrangement the structure-property study of their diketopyrrolopyrrole copolymers for organic photovoltaics
(2018-10-01)
Wu, Jhao-Lin
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Lin, Chiao-Wen
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Golder, Jan
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Lin, Tsu-Wei
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Chen, Chin-Ti
We have synthesized and characterized a series of diketopyrrolopyrrole (DPP)-oligothiophene copolymers, of which the number of regioregular oligothiophene ring (2T, 3T and 4T) and the arrangement of the alkyl side-chain on regioirregular quarterthiophene (4T0, 4T1 and 4T2) are variable. The side chains with regioregular lead to more planar copolymer backbones and higher short circuit current (J(sc)), but backbone torsion (due to regioirregular side chains) generates greater open-circuit voltages (V-OC) for DPP-oligothiophene copolymers. The increasing thiophene ring progressively raises HOMO energy level of copolymers but marginally affects their band gaps. Additionally, the HOMO energy level was found declined significantly with side-chain regioirregularity, because of reducing length of pi-conjugation. The HDDPP4T0 exhibits the strongest absorption, extensive network structure, and high hole mobility (mu(h )= 6.04 x 10(-4)cm(2)V(-1) s(-1)). These characteristics contribute to the exceptional high J(SC) of 18.96 mA/cm(2) for OPV with PCE = 6.12%. However, the HDDPP4T1 having an optimal combination of pi-conjugation and energy level affords the second highest V-OC (0.73 V) and the third highest J(SC) (16.89 mA/cm(2)), resulting the best PCE of 7.51% among all. X-ray scattering, transmission electron microscopy, atomic force microscopy, and space-charge-limited-current (SCLC) measurements reveal that the solvent additive of diphenylether (DPE) enables PC71BM-blended copolymers thin film in crystallinic fibril with enhanced hole mobility.
Polymer side-chain substituents elucidate thermochromism of benzodithiophene-dithiophenylacrylonitrile copolymers - polymer solubility correlation of thermochromism and photovoltaic performance
(2017-06-28)
Chen, Hung-Yang
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Lin, Chiao-Wen
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Chen, Chin-Ti
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Chen, Chao-Tsen
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Golder, Jan
Nine pBCNx polymers based on a donor-p-acceptor benzo[1,2-b:4,5-b']dithiophene-(E)-2,3-di(thiophen-2-yl) acrylonitrile main-chain structure and n-octyl/2-ethylhexyl as the side-chain substituents have been designed and synthesized. The thermochromism of the pBCNx polymers has been carefully examined in both solution and the thin-film state. With additional evidences from Raman spectroscopy and AFM microscopy, we have deciphered the varied colours of nine pBCNx polymers in solution and the pronounced thin-film thermochromism only observed for certain pBCNx polymers, i.e., pBCN4, pBCN5, pBCN6, and pBCN8. The alkyl side-chain, and hence the solubility or aggregation of pBCNx polymers, is a main factor of the varied colour in solution and the varied thermochromism in the thin film. We have identified that a stronger main-chain and main-chain interaction are present on the (E)-2,3-di(thiophen-2-yl) acrylonitrile moiety, whereas the poor to moderate solubility pBCN3, pBCN5', and pBCN7 exhibit pronounced thermochromism in solution, and pBCN4, pBCN5, pBCN6, and pBCN8 are four polymers which have good solubility in solution and show thermochromism in the thin-film state. We took navy blue pBCN3 (poor solubility), magenta pBCN4 (good solubility), and reddish purple pBCN5' (moderate solubility) for the fabrication of bulk heterojunction organic photovoltaics (OPVs). With a solvent annealing treatment, the power conversion efficiency of the OPVs has been improved significantly from 4.7% to 6.2% for the good solubility pBCN4, but there is little and no improvement for the moderate solubility pBCN5' and poor solubility pBCN3, respectively. Our study verifies that the good OPV performance of the pBCNx polymers can be correlated to the pronounced thin-film thermochromism. A good solubility of the polymer is a common characteristic of a material with significant thin-film thermochromism and good OPV performance.
SimCP3-An Advanced Homologue of SimCP2 as a Solution-Processed Small Molecular Host Material for Blue Phosphorescence Organic Light-Emitting Diodes
(2016-10-01)
Lee, Yi-Ting
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Chang, Yung-Ting
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Wu, Cheng-Lung
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Golder, Jan
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Chen, Chin-Ti
We have overcome the synthetic difficulty of 9,9',9 '',9 ''',9 '''',9 '''''-((phenylsilanetriyl) tris(benzene-5,3,1-triyl))hexakis(9H-carbazole) (SimCP3) an advanced homologue of previously known SimCP2 as a solution-processed, high triplet gap energy host material for a blue phosphorescence dopant. A series of organic light-emitting diodes based on blue phosphorescence dopant iridium (III) bis(4,6-difluorophenylpyridinato) picolate, FIrpic, were fabricated and tested to demonstrate the validity of solution-processed SimCP3 in the device fabrication.
Unconventional anode interlayer universally improving solar cell efficiency
(2018-08-08)
Golder, Jan
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Lin, Chiao-Wen
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Chen, Huan-Wen
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Lan, Yu-Bing
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Chen, Chin-Ti
Organic photovoltaic cells typically employ an interlayer sandwiched between the active donor or acceptor materials and the respective electrodes. Conventionally, the employed anode interlayer (AIL) adjacent to the anode has a wide optical band gap and a significantly higher lowest unoccupied molecular orbital (LUMO) energy level, compared to the adjunct electron donor material, such as boron subphthalocyanine chloride (SubPc) studied here. In this report, we synthesized three novel AIL materials, NP-beta-PCN, NPAPMLI and NPAPMLI, having narrow optical band gaps but matching the LUMO energy levels of SubPc in a planar heterojunction solar cell of ITO/SubPc/C-60/BCP/Al. Upon insertion of an ultrathin (2 nm) AIL, the device power conversion efficiency is increased from 3.98% to as high as 4.92%, mainly due to the significant increase of short-circuit current density (J(SC)) from 5.97 to 7.11-7.65 mA cm(-2). From the detailed morphological and photophysical studies, we have demonstrated that the employed unconventional materials of AIL are effective in exciton (of SubPc) blocking, thereby enhancing exciton diffusion towards the charge-separating interface of SubPc/C-60 and hence J(SC). Since these AIL materials all have a LUMO energy level very close to that of SubPc, the study reported here clarifies that the electron blocking is not a necessary property of an AIL material.