Electronic Properties of Polymer-Fullerene Solar Cells StudiedWith Light-Induced Electron Spin Resonance and Admittance Spectroscopy

2002 ◽  
Vol 725 ◽  
Author(s):  
V. Dyakonov ◽  
I. Riedel ◽  
Z. Chiguvare ◽  
C. Deibel ◽  
J. Parisi ◽  
...  
Keyword(s):  
Solar Cells ◽  
Electron Spin Resonance ◽  
Charge Transfer ◽  
Electron Spin ◽  
Spin Lattice Relaxation ◽  
Admittance Spectroscopy ◽  
Photoinduced Charge Transfer ◽  
Radical Species ◽  
Spin Resonance ◽  
Photoinduced Charge

AbstractWithin recent years, the development of polymer-fullerene plastic solar cells has made significant progress. In such devices, an efficient charge generation takes place via photoinduced charge transfer between the photoexcited conjugated polymer and acceptor-type fullerene molecules. Due to the paramagnetic nature of the radical species, the photoinduced charge transfer can be studied by means of light induced electron spin resonance (LESR) techniques. We carried out W-band (95 GHz) LESR at high magnetic field strengths. Two well separated line groups with a strong anisotropic structure were detected for the composite MDMOPPV: PCBM. From the line shape analysis, we obtained an environmental axial symmetry for the positive polaron P+ and a lower, rhomboedric symmetry for the fullerene anion. The signals were found to be independent of each other with different spin-lattice relaxation times; hence, the radical species can be investigated separately. In order to study the bulk transport properties, we carried out admittance spectroscopy on the ITO/PEDOT:PSS/MDMO-PPV:PCBM/Al device. Two frequency-dependent contributions to the device capacitance with the activation energies 9 meV and 177 meV were found. For the very shallow trap state, we assume a bulk impurity, whereas the latter one is assigned to an interfacial defect state, located at the composite- aluminium interface.

Electronic Properties of Polymer-Fullerene Solar Cells

2001 ◽  
Vol 665 ◽  
Author(s):  
V. Dyakonov ◽  
I. Riedel ◽  
C. Deibel ◽  
J. Parisi ◽  
C. J. Brabec ◽  
...  
Keyword(s):  
Solar Cells ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Fill Factor ◽  
Short Circuit ◽  
Open Circuit ◽  
Light Illumination ◽  
Positive Temperature ◽  
Admittance Spectroscopy ◽  
Spin Resonance

ABSTRACTWe studied the electronic transport properties of conjugated polymer/fullerene based solar cells by means of temperature and illumination intensity dependent current-voltage characteristics, admittance spectroscopy and light-induced electron spin resonance. The short-circuit current density increases with temperature at all light illumination intensities applied, i.e., from 100 mW/cm2 to 0.1 mW/cm2 (white light), whereas a temperature independent behavior was expected. An increase of the open-circuit voltage from 850 mV to 940 mV was observed, when cooling down the device from room temperature to 100 K. The fill factor depends strongly on temperature with a positive temperature coefficient in the whole temperature range. In contrast, the light intensity dependence of the fill factor shows a maximum of 52% at intermediate illumination intensities (3 mW/cm2) and decreases subsequently, when increasing the intensity up to 100 mW/cm2. Further studies by admittance spectroscopy revealed two frequency dependent contributions to the device capacitance. One, as we believe, originates from trapping states located at the interface between composite and metal electrode with an activation energy of EA=180 meV, and the other one is from very shallow bulk states with EA=10 meV. The origin of the latter is possibly the thermally activated conductivity. The photo-generation of charge carriers and their fate in these blends have been studied by light-induced electron spin resonance. We can clearly distinguish between photo-generated electrons and holes in the composites due to different spectroscopic splitting factors (g-factors). Additional information on the environmental axial symmetry of the holes located on the polymer chains as well as on a lower, rhombic, symmetry of the electrons located on the methanofullerene molecules has been obtained. The origin of the signals and parameters of the g-tensor have been confirmed from studies on a hole doped polymer.

scholarly journals Open-shell Donors and Closed-shell Acceptors in Organic Solar Cells

2021 ◽  
Author(s):  
Zhongxin Chen ◽  
Yuan Li ◽  
Wenqiang Li ◽  
Weiya Zhu ◽  
Miao Zeng ◽  
...  
Keyword(s):  
Solar Cells ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Organic Solar Cells ◽  
Ground State ◽  
Variable Temperature ◽  
Closed Shell ◽  
Open Shell ◽  
Singlet Ground State ◽  
Spin Resonance

The active materials of organic solar cells are widely recognized to show closed-shell singlet ground state and their electron spin resonance signals are attributed to the defects and impurities. Herein, we disclose the inherent open-shell singlet ground state of donors and the closed-shell structure of acceptors via the combination of variable temperature NMR, electron spin resonance, superconducting quantum interference device and theoretical calculation, providing a new perspective to understand the intrinsic molecular structure in organic solar cells.

Charge transfer in PDI-derived systems studied with light-induced electron spin resonance

2007 ◽  
Vol 157 (8-9) ◽  
pp. 363-367 ◽  
Author(s):  
Henryk Manikowski ◽  
Danuta Wróbel ◽  
Kornelia Lewandowska ◽  
Andrzej Graja
Keyword(s):  
Electron Spin Resonance ◽  
Charge Transfer ◽  
Electron Spin ◽  
Spin Resonance

scholarly journals Photoinduced charge carriers in conjugated polymer–fullerene composites studied with light-induced electron-spin resonance

1999 ◽  
Vol 59 (12) ◽  
pp. 8019-8025 ◽  
Author(s):  
V. Dyakonov ◽  
G. Zoriniants ◽  
M. Scharber ◽  
C. J. Brabec ◽  
R. A. J. Janssen ◽  
...  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Conjugated Polymer ◽  
Charge Carriers ◽  
Spin Resonance ◽  
Photoinduced Charge

Radiolysis of ethyl iodide and carbon tetrachloride mixtures at 77°K

1968 ◽  
Vol 46 (10) ◽  
pp. 1625-1632 ◽  
Author(s):  
R. M. Leblanc ◽  
F. C. Thyrion ◽  
J. A. Herman
Keyword(s):  
Electron Spin Resonance ◽  
Charge Transfer ◽  
Carbon Tetrachloride ◽  
Electron Spin ◽  
Ethyl Iodide ◽  
Ion Molecule Reactions ◽  
Positive Ions ◽  
Spin Resonance ◽  
Γ Rays ◽  
The Difference

The radical yields of C2H5• and CCl3• observed by electron spin resonance of CCl4 + C2H5I mixtures irradiated by γ rays at 77°K are compared with yields of HCl, I2, and HI measured after thawing. The dissociative capture of thermalized electrons by CCl4 is extremely effective and accounts for most of the observed radicals. The difference between yields of HCl and CCl3• results from charge transfer from C2H5I+ to CCl3•. The formation of iodine proceeds both from neutralization processes of Cl− ions with positive ions formed from C2H5I, and from ion–molecule reactions.

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