研究目的
To characterize the homogeneity of the external quantum efficiency in a free OPV roll-to-roll flexible solar module using microscopic techniques.
研究成果
The microscopic characterization revealed good local uniformity of EQE on a small scale (6-8% variation over 0.4 mm2) but significant cell-to-cell variations (up to 1.6 times difference in EQE peak values). Performance can be improved by optimizing printing uniformity and charge extraction efficiency of electrodes.
研究不足
The device showed degradation likely due to shipping and aging, with lower performance compared to pristine devices. Non-uniformities in EQE were observed, particularly near the electrons collecting electrode, possibly due to printing imperfections or non-uniform degradation. The study is limited to one module and specific microscopic techniques.
1：Experimental Design and Method Selection:
The study combines transmission and fluorescence microscopy to infer device structure, and confocal laser scanning microscopy to map photoluminescence (PL) and external quantum efficiency (EQE) on different length scales.
2：Sample Selection and Data Sources:
A 'freeOPV' module with an area of
3：0 × 2 cm2, consisting of 16 single cells connected in series, was used. List of Experimental Equipment and Materials:
Equipment includes a Keithley 2400 source meter for I-V measurements, a luxmeter for illumination monitoring, a Nikon Eclipse C1 Confocal Laser Scanning inverted microscope with a 20X DIC Plan Apochromat objective and
4：50 numerical aperture, an argon laser (488 nm line), a photo-multiplier (PMT) for PL detection, and a Stanford Research SR570 low-noise current preamplifier for photocurrent measurement. Materials include the OPV module and associated optical filters. Experimental Procedures and Operational Workflow:
I-V characteristics were measured under dark and sunlight conditions. PL and photocurrent maps were recorded simultaneously using the confocal microscope, with excitation at 488 nm, PL collected in backscattering configuration through a bandpass filter (655 ± 40 nm), and photocurrent measured in short circuit condition. Measurements were synchronized pixel by pixel with laser scanning.
5：Data Analysis Methods:
EQE was calculated as the ratio of extracted charge carriers to incident photons. Histograms and spatial distributions of EQE values were analyzed to assess homogeneity.
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Keithley 2400 source meter
2400
Keithley
Used for measuring current-voltage characteristics under dark and sunlight conditions.
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Stanford Research SR570 low-noise current preamplifier
SR570
Stanford Research
Used to measure the photocurrent signal in short circuit condition.
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luxmeter
Used to monitor illumination intensity during I-V measurements.
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Nikon Eclipse C1 Confocal Laser Scanning inverted microscope
Eclipse C1
Nikon
Used for confocal laser scanning microscopy to map photoluminescence and external quantum efficiency.
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argon laser
Used as the excitation source at 488 nm for the confocal microscope.
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photo-multiplier
PMT
Used to detect the photoluminescence signal in backscattering configuration.
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bandpass filter
Used to collect the photoluminescence signal in the 655 ± 40 nm range.
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