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Origin of photovoltaic effect in superconducting YBa2Cu3O6.96 ceramics.

Yang F, Han MY, Chang FG - Sci Rep (2015)

Bottom Line: The origin of the potential may be readily associated with the proximity effect at metal-superconductor interface when YBCO is superconducting and its value is estimated to be ~10(-8) mV at 50 K with a laser intensity of 502 mW/cm(2).Combination of a p-type material YBCO at normal state with an n-type material Ag-paste forms a quasi-pn junction which is responsible for the photovoltaic behavior of YBCO ceramics at high temperatures.Our findings may pave the way to new applications of photon-electronic devices and shed further light on the proximity effect at the superconductor-metal interface.

View Article: PubMed Central - PubMed

Affiliation: 1] College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007, P. R. China [2] Henan Key Laboratory of Photovoltaic Materials, Xinxiang 453007, P. R. China.

ABSTRACT
We report remarkable photovoltaic effect in YBa2Cu3O6.96 (YBCO) ceramic between 50 and 300 K induced by blue-laser illumination, which is directly related to the superconductivity of YBCO and the YBCO-metallic electrode interface. There is a polarity reversal for the open circuit voltage Voc and short circuit current Isc when YBCO undergoes a transition from superconducting to resistive state. We show that there exists an electrical potential across the superconductor-normal metal interface, which provides the separation force for the photo-induced electron-hole pairs. This interface potential directs from YBCO to the metal electrode when YBCO is superconducting and switches to the opposite direction when YBCO becomes nonsuperconducting. The origin of the potential may be readily associated with the proximity effect at metal-superconductor interface when YBCO is superconducting and its value is estimated to be ~10(-8) mV at 50 K with a laser intensity of 502 mW/cm(2). Combination of a p-type material YBCO at normal state with an n-type material Ag-paste forms a quasi-pn junction which is responsible for the photovoltaic behavior of YBCO ceramics at high temperatures. Our findings may pave the way to new applications of photon-electronic devices and shed further light on the proximity effect at the superconductor-metal interface.

No MeSH data available.


Related in: MedlinePlus

Photovoltaic characteristics as a function of laser intensity for YBCO-Ag paste system at 80 K.The laser spot center is positioned around the cathode electrodes (see Fig. 1i). a, I-V curves of YBCO irradiated with different laser intensities. b (top), Laser intensity dependence of open circuit voltage Voc and short circuit current Isc. The Isc values can not be obtained at low light intensity ( < 110 mW/cm2) because the I-V curves are parallel to the I-axis when the sample is in superconducting state. b (bottom), differential resistance as a function of laser intensity.
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f2: Photovoltaic characteristics as a function of laser intensity for YBCO-Ag paste system at 80 K.The laser spot center is positioned around the cathode electrodes (see Fig. 1i). a, I-V curves of YBCO irradiated with different laser intensities. b (top), Laser intensity dependence of open circuit voltage Voc and short circuit current Isc. The Isc values can not be obtained at low light intensity ( < 110 mW/cm2) because the I-V curves are parallel to the I-axis when the sample is in superconducting state. b (bottom), differential resistance as a function of laser intensity.

Mentions: To investigate the detailed evolution process of the photovoltaic properties during superconducting transition of YBCO, I-V curves of the sample at 80 K were measured with selected laser intensities illuminating at cathode electrode (Fig. 2). Without laser irradiation, the voltage across the sample keeps at zero regardless of current, indicating the superconducting state of the sample at 80 K (Fig. 2a). Similar to the data obtained at 50 K, I-V curves parallel to the I-axis moves downwards with increasing laser intensity until a critical value Pc is reached. Above this critical laser intensity (Pc), the superconductor undergoes a transition from a superconducting phase to a resistive phase; the voltage starts to increase with current due to the appearance of resistance in the superconductor. As a result, the I-V curve begins to intersect with the I-axis and V-axis leading to a negative Voc and a positive Isc at first. Now the sample seems to be in a special state in which the polarity of Voc and Isc is extremely sensitive to light intensity; with very small increase in light intensity Isc is converted from positive to negative and Voc from negative to positive value, passing the origin (the high sensitivity of photovoltaic properties, particularly the value of Isc, to light illumination can be seen more clearly in Fig. 2b). At the highest laser intensity available, the I-V curves intend to be parallel with each other, signifying the normal state of the YBCO sample.


Origin of photovoltaic effect in superconducting YBa2Cu3O6.96 ceramics.

Yang F, Han MY, Chang FG - Sci Rep (2015)

Photovoltaic characteristics as a function of laser intensity for YBCO-Ag paste system at 80 K.The laser spot center is positioned around the cathode electrodes (see Fig. 1i). a, I-V curves of YBCO irradiated with different laser intensities. b (top), Laser intensity dependence of open circuit voltage Voc and short circuit current Isc. The Isc values can not be obtained at low light intensity ( < 110 mW/cm2) because the I-V curves are parallel to the I-axis when the sample is in superconducting state. b (bottom), differential resistance as a function of laser intensity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4477232&req=5

f2: Photovoltaic characteristics as a function of laser intensity for YBCO-Ag paste system at 80 K.The laser spot center is positioned around the cathode electrodes (see Fig. 1i). a, I-V curves of YBCO irradiated with different laser intensities. b (top), Laser intensity dependence of open circuit voltage Voc and short circuit current Isc. The Isc values can not be obtained at low light intensity ( < 110 mW/cm2) because the I-V curves are parallel to the I-axis when the sample is in superconducting state. b (bottom), differential resistance as a function of laser intensity.
Mentions: To investigate the detailed evolution process of the photovoltaic properties during superconducting transition of YBCO, I-V curves of the sample at 80 K were measured with selected laser intensities illuminating at cathode electrode (Fig. 2). Without laser irradiation, the voltage across the sample keeps at zero regardless of current, indicating the superconducting state of the sample at 80 K (Fig. 2a). Similar to the data obtained at 50 K, I-V curves parallel to the I-axis moves downwards with increasing laser intensity until a critical value Pc is reached. Above this critical laser intensity (Pc), the superconductor undergoes a transition from a superconducting phase to a resistive phase; the voltage starts to increase with current due to the appearance of resistance in the superconductor. As a result, the I-V curve begins to intersect with the I-axis and V-axis leading to a negative Voc and a positive Isc at first. Now the sample seems to be in a special state in which the polarity of Voc and Isc is extremely sensitive to light intensity; with very small increase in light intensity Isc is converted from positive to negative and Voc from negative to positive value, passing the origin (the high sensitivity of photovoltaic properties, particularly the value of Isc, to light illumination can be seen more clearly in Fig. 2b). At the highest laser intensity available, the I-V curves intend to be parallel with each other, signifying the normal state of the YBCO sample.

Bottom Line: The origin of the potential may be readily associated with the proximity effect at metal-superconductor interface when YBCO is superconducting and its value is estimated to be ~10(-8) mV at 50 K with a laser intensity of 502 mW/cm(2).Combination of a p-type material YBCO at normal state with an n-type material Ag-paste forms a quasi-pn junction which is responsible for the photovoltaic behavior of YBCO ceramics at high temperatures.Our findings may pave the way to new applications of photon-electronic devices and shed further light on the proximity effect at the superconductor-metal interface.

View Article: PubMed Central - PubMed

Affiliation: 1] College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007, P. R. China [2] Henan Key Laboratory of Photovoltaic Materials, Xinxiang 453007, P. R. China.

ABSTRACT
We report remarkable photovoltaic effect in YBa2Cu3O6.96 (YBCO) ceramic between 50 and 300 K induced by blue-laser illumination, which is directly related to the superconductivity of YBCO and the YBCO-metallic electrode interface. There is a polarity reversal for the open circuit voltage Voc and short circuit current Isc when YBCO undergoes a transition from superconducting to resistive state. We show that there exists an electrical potential across the superconductor-normal metal interface, which provides the separation force for the photo-induced electron-hole pairs. This interface potential directs from YBCO to the metal electrode when YBCO is superconducting and switches to the opposite direction when YBCO becomes nonsuperconducting. The origin of the potential may be readily associated with the proximity effect at metal-superconductor interface when YBCO is superconducting and its value is estimated to be ~10(-8) mV at 50 K with a laser intensity of 502 mW/cm(2). Combination of a p-type material YBCO at normal state with an n-type material Ag-paste forms a quasi-pn junction which is responsible for the photovoltaic behavior of YBCO ceramics at high temperatures. Our findings may pave the way to new applications of photon-electronic devices and shed further light on the proximity effect at the superconductor-metal interface.

No MeSH data available.


Related in: MedlinePlus