研究目的
Investigating the robustness of transient photovoltage/current (TPV/C) and impedance spectroscopy (IS) techniques for quantifying charge carrier density in organic solar cells under light irradiation, especially in the presence of geometric capacitance interference.
研究成果
TPV/C is more robust than IS for quantifying charge carrier density in organic solar cells, especially in PHJ structures with significant geometric capacitance contributions. Accurate estimation of charge carrier density, lifetime, and distribution is crucial for understanding the link between donor/acceptor interfacial structure and charge carrier recombination kinetics.
研究不足
The study highlights the difficulty of IS in separating charge carriers in the organic layer from those in the electrodes for PHJ cells with large geometric capacitance contributions. The accuracy of charge carrier density and lifetime measurements can be affected by the error in equivalent circuit fitting of IS.
1：Experimental Design and Method Selection:
The study compares TPV/C and IS techniques for evaluating charge carrier density in organic solar cells with bulk heterojunction (BHJ) and planar heterojunction (PHJ) structures.
2：Sample Selection and Data Sources:
BHJ and PHJ solar cells were prepared using poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as donor and acceptor materials, respectively.
3：List of Experimental Equipment and Materials:
Equipment includes a white light-emitting diode (LED) for steady light irradiation, a
4：4 ns pulsed laser for perturbation, and neutral-density filters for light intensity tuning. Experimental Procedures and Operational Workflow:
TPV/C measurements were performed under steady light irradiation with perturbation by a pulsed laser. IS measurements were conducted with an external DC voltage equal to VOC and a superimposing AC voltage.
5：Data Analysis Methods:
The differential capacitance was calculated from TPV/C data, and impedance response was analyzed by equivalent circuit fitting for IS data.
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