Charlotte, NC, United States
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Ortiz A.L.,Burson 200 | Collier G.S.,Burson 200 | Marin D.M.,Burson 200 | Kassel J.A.,Burson 200 | And 3 more authors.
Journal of Materials Chemistry C | Year: 2015

The singlet exciton diffusion properties of solution-cast thin films prepared from mixed substituent monoiodophenyl or monobromophenyl derivatives of 5,10,15,20-tetrakis(4-carbomethoxyphenyl)porphyrin (TCM4PP) were investigated for use in solar energy conversion applications. The photoluminescent singlet decay lifetime PL(t) of pristine porphyrin films and films lightly doped (0.1-0.6% wt) with [6,6]-phenyl-C61-butryic acid methyl ester (PCBM) were used to obtain relative quenching efficiencies (Q). The exciton diffusion coefficient (D) and exciton diffusion length (LD) for each derivative were obtained by modeling the quenching efficiency and PL lifetime decay data using a 3D exciton Monte Carlo diffusion simulation. Although the three TCMPP derivatives showed nearly identical absorbances and electrochemical properties, the monobromophenyl or monoiodophenyl substituted porphyrins exhibited significantly lower steady-state emission intensities and fluorescent lifetimes in solution. Amorphous thin films of the halogenated derivatives also exhibited a decrease in the PL decay lifetimes, relative quenching efficiencies, and reduced singlet exciton diffusion lengths. The singlet exciton diffusion length for TCM4PP was calculated to be 15 nm and decreased by 71% to 4.4 nm for TCM3IPP with the addition of a single iodo substituent. Photocurrent-voltage measurements of the derivatives in a PCBM bulk heterojunction device suggest that lowered exciton diffusion and enhanced singlet to triplet exciton conversion, due to the heavy atom effect, decreases photoconversion efficiency. This journal is © 2015 The Royal Society of Chemistry.


Kaushal M.,Burson 200 | Ortiz A.L.,Burson 200 | Kassel J.A.,Burson 200 | Hall N.,Burson 200 | And 3 more authors.
Journal of Materials Chemistry C | Year: 2016

The effects of molecular arrangement on the singlet exciton diffusion properties of free-base carboalkoxyphenylporphyrins containing a variety of alkyl substituents were investigated in solution-cast thin films. Exciton diffusivity was calculated using relative quenching efficiencies (Q) obtained by measuring the singlet photoluminescent decay lifetime PL(t) of pristine porphyrin films and films doped with 0.06-0.2% volume fraction of [6,6]-phenyl-C61-butryic acid methyl ester (PCBM). The quenching efficiency and PL lifetime decay data was used in a 3D exciton diffusion Monte Carlo simulation model to extract the exciton diffusion coefficient (D) and diffusion length (LD). Five carboalkoxyphenyl porphyrins (TCAPPs) were synthesized and analyzed in solution-cast thin films, tetra(4-carbomethoxyphenyl)porphyrin (TCM4PP), tetra(4-carbobutoxyphenyl) porphyrin (TCB4PP), tetra(4-carbohexoxyphenyl)porphyrin (TCH4PP), tetra(4-carbo-2-ethylhexoxyphenyl) porphyrin (TCEH4PP), and tetra(4-carbooctoxyphenyl)porphyrin (TCO4PP). Longer alkyl chain derivatives yielded increased PL decay lifetimes and extended the exciton diffusion lengths (LD) for octyl (TCO4PP) and hexyl (TCH4PP) porphyrin derivatives. We observed an increase in the LD from 15 nm for TCM4PP to 25 nm for TCH4PP, while a branched alkyl chain derivative (TCEH4PP) showed the lowest LD of 14 nm. UV-Vis and XRD data indicate that molecular organization is strongly dependent upon the peripheral carboalkoxy chain, and that nematic molecular organization resulted in an increase in the exciton diffusion length. Our findings are an important step toward a deeper understanding of the exciton diffusivity and molecular packing relationship of simple free-base porphyrins. © 2016 The Royal Society of Chemistry.


Marin D.M.,Burson 200 | Payerpaj S.,Burson 200 | Collier G.S.,Burson 200 | Ortiz A.L.,Burson 200 | And 3 more authors.
Physical Chemistry Chemical Physics | Year: 2015

Sensitizers with high triplet quantum yields are useful for generating photovoltaics, photocatalysts and photodynamic therapy agents with increased efficiency. In this study, the heavy atom effect was used to optimize the triplet and singlet oxygen quantum yields of 5,10,15,20-tetrakis(4-carbomethoxyphenyl)porphyrin (1-TCM4PP). The triplet quantum yields, determined using delayed fluorescence, was calculated as 0.35 for 1-TCM4PP, 0.75 for 5,10,15-tris(4-carbomethoxyphenyl)-20-(4-bromophenyl)porphyrin (2-TBCM3PP) and 0.88 for 5,10,15-tris(4-carbomethoxyphenyl)-20-(4-iodophenyl)porphyrin (3-TCM3IPP). Chemical quenching of 1,3-diphenylisobenzofuran and singlet oxygen emission studies rendered an average singlet oxygen quantum yield of 0.51, 0.75, and 0.90 for TCM4PP, TBCM3PP and TCM3IPP respectively. These photophysical properties indicate that a single halogen atom is capable of transforming TCM4PP into a sensitizer with strong triplet character. This is useful for generating singlet oxygen for photodynamic therapy, creating a long lasting reactive species for catalysis and for extending diffusion lengths in photovoltaic applications while retaining three molecular modification points for further functionalization. This journal is © the Owner Societies.


Sensitizers with high triplet quantum yields are useful for generating photovoltaics, photocatalysts and photodynamic therapy agents with increased efficiency. In this study, the heavy atom effect was used to optimize the triplet and singlet oxygen quantum yields of 5,10,15,20-tetrakis(4-carbomethoxyphenyl)porphyrin (1-TCM4PP). The triplet quantum yields, determined using delayed fluorescence, was calculated as 0.35 for 1-TCM4PP, 0.75 for 5,10,15-tris(4-carbomethoxyphenyl)-20-(4-bromophenyl)porphyrin (2-TBCM3PP) and 0.88 for 5,10,15-tris(4-carbomethoxyphenyl)-20-(4-iodophenyl)porphyrin (3-TCM3IPP). Chemical quenching of 1,3-diphenylisobenzofuran and singlet oxygen emission studies rendered an average singlet oxygen quantum yield of 0.51, 0.75, and 0.90 for TCM4PP, TBCM3PP and TCM3IPP respectively. These photophysical properties indicate that a single halogen atom is capable of transforming TCM4PP into a sensitizer with strong triplet character. This is useful for generating singlet oxygen for photodynamic therapy, creating a long lasting reactive species for catalysis and for extending diffusion lengths in photovoltaic applications while retaining three molecular modification points for further functionalization.

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