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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

I-V characteristics of YBa2Cu3O6.96 illuminated by blue laser (λ = 450 nm) at 50 K(a–c) and 300 K (e–g). Values of V(I) were obtained by sweeping the current from −10 mA to +10 mA in vacuum. Only part of the experimental data is presented for the sake of clarity. a, Current-voltage characteristics of YBCO measured with laser spot positioned at the cathode (i). All the I-V curves are horizontal straight lines indicating the sample is still superconducting with laser irradiation. The curve moves down with increasing laser intensity, indicating that there exist a negative potential (Voc) between the two voltage leads even with zero current. The I-V curves remain unchanged when the laser is directed at the center of the sample at ether 50 K (b) or 300 K (f). The horizontal line moves up as the anode is illuminated (c). A schematic model of metal-superconductor junction at 50 K is shown in d. Current-voltage characteristics of normal state YBCO at 300 K measured with laser beam pointed at cathode and anode are given in e and g respectively. In contrast to the results at 50 K, non-zero slope of the straight lines indicates that YBCO is in normal state; the values of Voc vary with light intensity in an opposite direction, indicating a different charge separation mechanism. A possible interface structure at 300 K is depicted in h. j. The real picture of the sample with leads.
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f1: I-V characteristics of YBa2Cu3O6.96 illuminated by blue laser (λ = 450 nm) at 50 K(a–c) and 300 K (e–g). Values of V(I) were obtained by sweeping the current from −10 mA to +10 mA in vacuum. Only part of the experimental data is presented for the sake of clarity. a, Current-voltage characteristics of YBCO measured with laser spot positioned at the cathode (i). All the I-V curves are horizontal straight lines indicating the sample is still superconducting with laser irradiation. The curve moves down with increasing laser intensity, indicating that there exist a negative potential (Voc) between the two voltage leads even with zero current. The I-V curves remain unchanged when the laser is directed at the center of the sample at ether 50 K (b) or 300 K (f). The horizontal line moves up as the anode is illuminated (c). A schematic model of metal-superconductor junction at 50 K is shown in d. Current-voltage characteristics of normal state YBCO at 300 K measured with laser beam pointed at cathode and anode are given in e and g respectively. In contrast to the results at 50 K, non-zero slope of the straight lines indicates that YBCO is in normal state; the values of Voc vary with light intensity in an opposite direction, indicating a different charge separation mechanism. A possible interface structure at 300 K is depicted in h. j. The real picture of the sample with leads.

Mentions: Figure 1a–c shows that the I-V characteristics of YBCO ceramic sample at 50 K. Without light illumination, the voltage across the sample remains at zero with changing current, as can be expected from a superconducting material. Obvious photovoltaic effect appears when laser beam is directed at cathode (Fig. 1a): the I-V curves parallel to the I-axis moves downwards with increasing laser intensity. It is evident that there is a negative photo-induced voltage even without any current (often called open circuit voltage Voc). The zero slope of the I-V curve indicates that the sample is still superconducting under laser illumination.


Origin of photovoltaic effect in superconducting YBa2Cu3O6.96 ceramics.

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

I-V characteristics of YBa2Cu3O6.96 illuminated by blue laser (λ = 450 nm) at 50 K(a–c) and 300 K (e–g). Values of V(I) were obtained by sweeping the current from −10 mA to +10 mA in vacuum. Only part of the experimental data is presented for the sake of clarity. a, Current-voltage characteristics of YBCO measured with laser spot positioned at the cathode (i). All the I-V curves are horizontal straight lines indicating the sample is still superconducting with laser irradiation. The curve moves down with increasing laser intensity, indicating that there exist a negative potential (Voc) between the two voltage leads even with zero current. The I-V curves remain unchanged when the laser is directed at the center of the sample at ether 50 K (b) or 300 K (f). The horizontal line moves up as the anode is illuminated (c). A schematic model of metal-superconductor junction at 50 K is shown in d. Current-voltage characteristics of normal state YBCO at 300 K measured with laser beam pointed at cathode and anode are given in e and g respectively. In contrast to the results at 50 K, non-zero slope of the straight lines indicates that YBCO is in normal state; the values of Voc vary with light intensity in an opposite direction, indicating a different charge separation mechanism. A possible interface structure at 300 K is depicted in h. j. The real picture of the sample with leads.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: I-V characteristics of YBa2Cu3O6.96 illuminated by blue laser (λ = 450 nm) at 50 K(a–c) and 300 K (e–g). Values of V(I) were obtained by sweeping the current from −10 mA to +10 mA in vacuum. Only part of the experimental data is presented for the sake of clarity. a, Current-voltage characteristics of YBCO measured with laser spot positioned at the cathode (i). All the I-V curves are horizontal straight lines indicating the sample is still superconducting with laser irradiation. The curve moves down with increasing laser intensity, indicating that there exist a negative potential (Voc) between the two voltage leads even with zero current. The I-V curves remain unchanged when the laser is directed at the center of the sample at ether 50 K (b) or 300 K (f). The horizontal line moves up as the anode is illuminated (c). A schematic model of metal-superconductor junction at 50 K is shown in d. Current-voltage characteristics of normal state YBCO at 300 K measured with laser beam pointed at cathode and anode are given in e and g respectively. In contrast to the results at 50 K, non-zero slope of the straight lines indicates that YBCO is in normal state; the values of Voc vary with light intensity in an opposite direction, indicating a different charge separation mechanism. A possible interface structure at 300 K is depicted in h. j. The real picture of the sample with leads.
Mentions: Figure 1a–c shows that the I-V characteristics of YBCO ceramic sample at 50 K. Without light illumination, the voltage across the sample remains at zero with changing current, as can be expected from a superconducting material. Obvious photovoltaic effect appears when laser beam is directed at cathode (Fig. 1a): the I-V curves parallel to the I-axis moves downwards with increasing laser intensity. It is evident that there is a negative photo-induced voltage even without any current (often called open circuit voltage Voc). The zero slope of the I-V curve indicates that the sample is still superconducting under laser illumination.

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