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Tikunena za mphamvu yodabwitsa ya photovoltaic mu YBa2Cu3O6.96 (YBCO) ceramic pakati pa 50 ndi 300 K yoyambitsidwa ndi kuwala kwa blue-laser, komwe kumakhudzana mwachindunji ndi superconductivity ya YBCO ndi YBCO-metallic electrode interface. Pali kusintha kwa polarity kwa voliyumu yotseguka ya Voc ndi short circuit current Isc pamene YBCO ikusintha kuchoka pa superconducting kupita ku resistive state. Tikuwonetsa kuti pali mphamvu yamagetsi kudutsa superconductor-normal metal interface, yomwe imapereka mphamvu yolekanitsa mawiri a electron-hole omwe amapangidwa ndi photo-induced. Mphamvu iyi ya interface imatsogolera kuchokera ku YBCO kupita ku metal electrode pamene YBCO ikupanga superconducting ndipo imasinthira mbali ina pamene YBCO ikukhala yosapanga superconducting. Chiyambi cha mphamvuyi chingagwirizane mosavuta ndi mphamvu yapafupi pa metal-superconductor interface pamene YBCO ikupanga superconducting ndipo mtengo wake ukuyembekezeka kukhala ~10–8 mV pa 50 K ndi mphamvu ya laser ya 502 mW/cm2. Kuphatikiza kwa chinthu cha mtundu wa p YBCO chomwe chili bwino ndi chinthu cha mtundu wa n Ag-paste imapanga malo olumikizirana a quasi-pn omwe amachititsa kuti zinthu za YBCO ceramics zisinthe pa kutentha kwambiri. Zomwe tapeza zitha kuyambitsa njira yatsopano yogwiritsira ntchito zida zamagetsi za photon ndikuwunikiranso momwe zimakhalira pafupi ndi chipangizo cha superconductor-metal.
Mphamvu yamagetsi yochokera ku zithunzi mu ma superconductor otentha kwambiri yanenedwa kumayambiriro kwa zaka za m'ma 1990 ndipo yafufuzidwa kwambiri kuyambira pamenepo, komabe mtundu wake ndi momwe amagwirira ntchito sizinakhazikike1,2,3,4,5. Makanema owonda a YBa2Cu3O7-δ (YBCO)6,7,8, makamaka, amaphunziridwa kwambiri mu mawonekedwe a selo ya photovoltaic (PV) chifukwa cha kusiyana kwake kwa mphamvu kosinthika9,10,11,12,13. Komabe, kukana kwakukulu kwa substrate nthawi zonse kumabweretsa mphamvu yochepa yosinthira chipangizocho ndipo kumabisa makhalidwe akuluakulu a PV a YBCO8. Pano tikunena za mphamvu yodabwitsa ya photovoltaic yomwe imabwera chifukwa cha kuwala kwa blue-laser (λ = 450 nm) mu ceramic ya YBa2Cu3O6.96 (YBCO) pakati pa 50 ndi 300 K (Tc ~ 90 K). Tikuwonetsa kuti mphamvu ya PV ikugwirizana mwachindunji ndi mphamvu ya YBCO komanso mtundu wa mawonekedwe a electrode ya YBCO-metallic. Pali kusintha kwa polarity kwa voteji ya open circuit Voc ndi short circuit current Isc pamene YBCO ikusintha kuchoka pa superconducting phase kupita ku resistive state. Akuti pali mphamvu yamagetsi kudutsa superconductor-normal metal interface, yomwe imapereka mphamvu yolekanitsa ma electron-hole pairs omwe amapangidwa ndi photo-induced. Mphamvu ya interface iyi imatsogolera kuchokera ku YBCO kupita ku metal electrode pamene YBCO ikupanga superconducting ndipo imasinthira mbali ina pamene chitsanzocho sichikupanga superconducting. Chiyambi cha mphamvuyi chikhoza kugwirizanitsidwa mwachibadwa ndi proximity effect14,15,16,17 pa metal-superconductor interface pamene YBCO ikupanga superconducting ndipo mtengo wake ukuyembekezeka kukhala ~10−8 mV pa 50 K ndi mphamvu ya laser ya 502 mW/cm2. Kuphatikiza kwa p-type material YBCO pa normal state ndi n-type material Ag-paste imapanga, mwina, quasi-pn junction yomwe imayambitsa khalidwe la PV la YBCO ceramics pa kutentha kwakukulu. Zomwe tawona zatithandiza kudziwa bwino chiyambi cha mphamvu ya PV mu ma ceramics a YBCO omwe amapangidwa ndi kutentha kwambiri ndipo zathandiza kuti igwiritsidwe ntchito mu zipangizo zamagetsi monga chowunikira kuwala mwachangu, etc.
Chithunzi 1a–c chikuwonetsa kuti makhalidwe a IV a chitsanzo cha YBCO ceramic pa 50 K. Popanda kuunika kwa kuwala, magetsi odutsa mu chitsanzo amakhalabe pa zero ndi kusintha kwa mphamvu, monga momwe zingayembekezeredwe kuchokera ku chinthu chowongolera mphamvu. Mphamvu yowonekera ya photovoltaic imawonekera pamene kuwala kwa laser kulunjika ku cathode (Chithunzi 1a): ma curve a IV ofanana ndi I-axis amatsika pansi ndi mphamvu yowonjezera ya laser. N'zoonekeratu kuti pali magetsi olakwika omwe amapangidwa ndi photo ngakhale opanda mphamvu iliyonse (nthawi zambiri amatchedwa voliyumu yotseguka ya Voc). Kutsetsereka kwa zero kwa IV curve kumasonyeza kuti chitsanzocho chikadali superconducting pansi pa kuwala kwa laser.
(a–c) ndi 300 K (e–g). Ma values a V(I) adapezeka poyesa mphamvu yamagetsi kuchokera pa −10 mA mpaka +10 mA mu vacuum. Gawo lokha la deta yoyesera limaperekedwa kuti limveke bwino. a, Makhalidwe a magetsi a YBCO omwe amayesedwa ndi malo a laser omwe ali pa cathode (i). Ma curve onse a IV ndi mizere yolunjika yopingasa yomwe ikusonyeza kuti chitsanzocho chikupitilizabe kuyendetsedwa ndi kuwala kwa laser. Mzerewo umatsika ndi mphamvu ya laser yowonjezereka, zomwe zikusonyeza kuti pali mphamvu yoipa (Voc) pakati pa ma voltage lead awiri ngakhale ndi zero current. Ma IV curve sasintha pamene laser ikuyang'aniridwa pakati pa chitsanzocho pa ether 50 K (b) kapena 300 K (f). Mzere wopingasa umakwera mmwamba pamene anode ikuwunikiridwa (c). Chitsanzo cha schematic cha chitsulo-superconductor junction pa 50 K chikuwonetsedwa mu d. Makhalidwe a magetsi a YBCO pa 300 K omwe amayesedwa ndi kuwala kwa laser komwe kumalunjika pa cathode ndi anode amaperekedwa mu e ndi g motsatana. Mosiyana ndi zotsatira za 50 K, kutsetsereka kosakhala zero kwa mizere yowongoka kumasonyeza kuti YBCO ili mu mkhalidwe wabwinobwino; ma values a Voc amasiyana ndi mphamvu ya kuwala kumbali ina, kusonyeza njira yosiyana yolekanitsira ma charge. Kapangidwe kolumikizana komwe kangakhalepo pa 300 K kakuwonetsedwa mu hj Chithunzi chenicheni cha chitsanzo chokhala ndi ma lead.
YBCO yolemera mu okosijeni mu superconducting state imatha kuyamwa pafupifupi mtundu wonse wa kuwala kwa dzuwa chifukwa cha kusiyana kwake kochepa kwa mphamvu (Eg)9,10, motero kupanga ma electron-hole pairs (e-h). Kuti apange voteji yotseguka ya Voc mwa kuyamwa ma photon, ndikofunikira kulekanitsa ma eh pairs opangidwa ndi photo musanayambe kuyanjananso18. Voc yoyipa, poyerekeza ndi cathode ndi anode monga momwe zasonyezedwera mu Chithunzi 1i, ikusonyeza kuti pali mphamvu yamagetsi kudutsa mawonekedwe achitsulo-superconductor, omwe amasuntha ma elekitironi kupita ku anode ndi mabowo kupita ku cathode. Ngati ndi choncho, payeneranso kukhala mphamvu yoloza kuchokera ku superconductor kupita ku electrode yachitsulo pa anode. Chifukwa chake, Voc yabwino ingapezeke ngati dera lachitsanzo pafupi ndi anode lawunikiridwa. Kuphatikiza apo, sipayenera kukhala ma voltages opangidwa ndi photo pamene malo a laser akuloza kumadera akutali ndi ma electrode. Ndi momwemo monga momwe tingawonere mu Chithunzi 1b,c!.
Pamene malo owala asuntha kuchokera ku electrode ya cathode kupita pakati pa chitsanzo (pafupifupi 1.25 mm kutali ndi malo olumikizirana), palibe kusintha kwa ma curve a IV ndipo palibe Voc yomwe ingawonekere ndi mphamvu ya laser yowonjezereka kufika pamtengo wapamwamba womwe ulipo (Chithunzi 1b). Mwachibadwa, zotsatirazi zitha kufotokozedwa chifukwa cha nthawi yochepa ya moyo wa zonyamulira zomwe zimayambitsidwa ndi zithunzi komanso kusowa kwa mphamvu yolekanitsa mu chitsanzo. Mawiri a electron-hole amatha kupangidwa nthawi iliyonse yomwe chitsanzocho chawunikiridwa, koma ambiri mwa mawiri a e-h adzawonongedwa ndipo palibe mphamvu ya photovoltaic yomwe imawoneka ngati malo a laser agwera m'malo omwe ali kutali ndi ma electrode aliwonse. Kusuntha malo a laser kupita ku ma electrode a anode, ma curve a IV omwe ali ofanana ndi I-axis amakwera mmwamba ndi mphamvu ya laser yowonjezereka (Chithunzi 1c). Malo ofanana amagetsi omwe ali mkati mwake alipo mu gawo la zitsulo-superconductor pa anode. Komabe, electrode yachitsulo imalumikizana ndi positive lead ya dongosolo loyesera nthawi ino. Mabowo opangidwa ndi laser amakankhidwira ku anode lead motero Voc yabwino imawonekera. Zotsatira zomwe zaperekedwa pano zikupereka umboni wamphamvu wakuti pali njira yolumikizirana yolunjika kuchokera ku superconductor kupita ku electrode yachitsulo.
Mphamvu ya Photovoltaic mu ma ceramics a YBa2Cu3O6.96 pa 300 K ikuwonetsedwa mu Chithunzi 1e–g. Popanda kuunikira kwa kuwala, IV curve ya chitsanzo ndi mzere wowongoka womwe umadutsa komwe kumayambira. Mzere wowongoka uwu umapita mmwamba molingana ndi woyamba ndi mphamvu yowonjezera ya laser yomwe ikuwalira pa ma cathode leads (Chithunzi 1e). Pali milandu iwiri yochepetsera chidwi cha chipangizo cha photovoltaic. Mkhalidwe wa short-circuit umachitika pamene V = 0. Mphamvu yamagetsi pankhaniyi imatchedwa short circuit current (Isc). Mkhalidwe wachiwiri wochepetsera ndi mkhalidwe wa open-circuit (Voc) womwe umachitika pamene R→∞ kapena current ili zero. Chithunzi 1e chikuwonetsa momveka bwino kuti Voc ndi yabwino ndipo imawonjezeka ndi mphamvu yowonjezera ya kuwala, mosiyana ndi zotsatira zomwe zapezeka pa 50 K; pomwe Isc yoyipa imawoneka ikuwonjezeka ndi kuunikira kwa kuwala, khalidwe lachizolowezi la maselo abwinobwino a dzuwa.
Mofananamo, pamene kuwala kwa laser kukuloza kumadera akutali ndi ma electrode, curve ya V(I) siimasiyana ndi mphamvu ya laser ndipo palibe mphamvu ya photovoltaic yomwe imawonekera (Chithunzi 1f). Mofanana ndi muyeso wa 50 K, ma curve a IV amasunthira mbali ina pamene electrode ya anode ikuwotchedwa (Chithunzi 1g). Zotsatira zonsezi zomwe zapezeka pa dongosolo la YBCO-Ag paste pa 300 K yokhala ndi laser yowotchedwa pamalo osiyanasiyana a chitsanzocho zimagwirizana ndi kuthekera kwa mawonekedwe kosiyana ndi komwe kumawoneka pa 50 K.
Ma electron ambiri amaundana mu ma Cooper pairs mu superconducting YBCO pansi pa kutentha kwake kosinthira Tc. Ali mu electrode yachitsulo, ma electron onse amakhalabe mu mawonekedwe amodzi. Pali kuchuluka kwakukulu kwa ma electron amodzi ndi ma Cooper pairs pafupi ndi mawonekedwe a metal-superconductor. Ma electron ambiri onyamula amodzi muzinthu zachitsulo amafalikira m'dera la superconductor, pomwe ma Cooper-pairs ambiri onyamula amodzi m'dera la YBCO amafalikira m'dera lachitsulo. Pamene ma Cooper awiriawiri akunyamula ma charges ambiri komanso okhala ndi kuyenda kwakukulu kuposa ma electron amodzi akufalikira kuchokera ku YBCO kupita ku dera lachitsulo, ma atomu omwe ali ndi positive charge amasiyidwa, zomwe zimapangitsa kuti pakhale gawo lamagetsi m'dera la space charge. Kulunjika kwa gawo lamagetsi ili kukuwonetsedwa mu chithunzi cha schematic Chithunzi 1d. Kuunikira kwa photon pafupi ndi dera la space charge kungapangitse ma eh pairs omwe adzalekanitsidwa ndikuchotsedwa ndikupanga photocurrent mu reverse-bias direction. Ma electron akangotuluka m'munda wamagetsi womangidwa, amaundana kukhala awiriawiri ndikuyenda kupita ku electrode ina popanda kukana. Pankhaniyi, Voc ili moyang'anizana ndi polarity yomwe idakhazikitsidwa kale ndipo imawonetsa mtengo woyipa pamene kuwala kwa laser kulunjika kudera lozungulira electrode yoyipa. Kuchokera pamtengo wa Voc, mphamvu yodutsa mu mawonekedwe imatha kuyerekezeredwa: mtunda pakati pa ma lead awiri a voltage d ndi ~5 × 10−3 m, makulidwe a mawonekedwe a metal-superconductor, di, ayenera kukhala ofanana ndi kutalika kwa mgwirizano wa YBCO superconductor (~1 nm)19,20, tengani mtengo wa Voc = 0.03 mV, ma Vms omwe angatheke pa mawonekedwe a metal-superconductor amayesedwa kukhala ~10−11 V pa 50 K ndi mphamvu ya laser ya 502 mW/cm2, pogwiritsa ntchito equation,
Tikufuna kutsindika apa kuti mphamvu yamagetsi yochokera ku photo-induced siyingathe kufotokozedwa ndi mphamvu ya kutentha kwa chithunzi. Zatsimikiziridwa mwa kuyesa kuti mphamvu ya Seebeck ya superconductor YBCO ndi Ss = 021. Mphamvu ya Seebeck ya mawaya a mkuwa ili pakati pa SCu = 0.34–1.15 μV/K3. Kutentha kwa waya wamkuwa pamalo a laser kumatha kukwezedwa ndi mphamvu yaying'ono ya 0.06 K ndi mphamvu yayikulu ya laser yomwe ikupezeka pa 50 K. Izi zitha kupanga mphamvu ya thermoelectric ya 6.9 × 10−8 V yomwe ndi yaying'ono kwambiri kuposa Voc yomwe yapezeka mu Chithunzi 1 (a). N'zoonekeratu kuti mphamvu ya thermoelectric ndi yaying'ono kwambiri kuti ifotokoze zotsatira za kuyesa. Ndipotu, kusintha kwa kutentha chifukwa cha kuwala kwa laser kumatha mkati mwa mphindi imodzi kuti phindu lochokera ku mphamvu ya kutentha linyalanyazidwe mosamala.
Mphamvu ya photovoltaic ya YBCO pa kutentha kwa chipinda ikuwonetsa kuti njira yosiyana yolekanitsira ma charge ikugwiritsidwa ntchito pano. Superconducting YBCO mu mkhalidwe wabwinobwino ndi chinthu cha mtundu wa p chokhala ndi mabowo ngati chonyamulira ma charge22,23, pomwe Ag-paste yachitsulo ili ndi mawonekedwe a chinthu cha mtundu wa n. Mofanana ndi ma pn junctions, kufalikira kwa ma electron mu siliva phala ndi mabowo mu YBCO ceramic kudzapanga munda wamagetsi wamkati womwe ukulozera ku YBCO ceramic pamalo olumikizirana (Chithunzi 1h). Ndi munda wamkati uwu womwe umapereka mphamvu yolekanitsa ndipo umatsogolera ku Voc yabwino ndi negative Isc ya dongosolo la YBCO-Ag pa kutentha kwa chipinda, monga momwe zasonyezedwera mu Chithunzi 1e. Kapenanso, Ag-YBCO ikhoza kupanga p-type Schottky junction yomwe imatsogoleranso ku interface potential yokhala ndi polarity yofanana ndi yomwe ili mu chitsanzo chomwe chaperekedwa pamwambapa24.
Kuti afufuze mwatsatanetsatane njira yosinthira mphamvu za photovoltaic panthawi yosinthira kwa superconducting ya YBCO, ma curve a IV a chitsanzo pa 80 K adayesedwa ndi mphamvu ya laser yosankhidwa yomwe imawunikira pa cathode electrode (Chithunzi 2). Popanda kuwala kwa laser, voltage kudutsa chitsanzocho imasunga pa zero mosasamala kanthu za mphamvu yamagetsi, kusonyeza mkhalidwe wa superconducting wa chitsanzo pa 80 K (Chithunzi 2a). Mofanana ndi deta yomwe yapezeka pa 50 K, ma curve a IV ofanana ndi I-axis amatsika pansi ndi mphamvu ya laser yowonjezera mpaka Pc yamtengo wapatali itafika. Pamwamba pa mphamvu ya laser yofunika iyi (Pc), superconductor imadutsa kusintha kuchokera ku gawo la superconducting kupita ku gawo loletsa; voltage imayamba kuwonjezeka ndi mphamvu yamagetsi chifukwa cha kuwoneka kwa kukana mu superconductor. Zotsatira zake, curve ya IV imayamba kuyanjana ndi I-axis ndi V-axis zomwe zimapangitsa kuti Voc yoyipa ndi Isc yabwino poyamba. Tsopano chitsanzocho chikuwoneka kuti chili mu mkhalidwe wapadera momwe polarity ya Voc ndi Isc imakhudzidwa kwambiri ndi mphamvu ya kuwala; Ndi kuwonjezeka kochepa kwambiri kwa mphamvu ya kuwala, Isc imasinthidwa kuchoka pa zabwino kupita pa zoipa ndipo Voc kuchokera pa zoyipa kupita pa zabwino, zomwe zimapangitsa kuti chiyambi chake chikhale chosavuta (kukhudzidwa kwakukulu kwa mphamvu ya photovoltaic, makamaka mtengo wa Isc, kupita ku kuwala kwa kuwala kungawonekere bwino mu Chithunzi 2b). Pa mphamvu yapamwamba kwambiri ya laser yomwe ilipo, ma curve a IV akufuna kukhala ofanana, kusonyeza momwe chitsanzo cha YBCO chilili.
Malo ozungulira laser ali mozungulira ma electrode a cathode (onani Chithunzi 1i). a, ma curve a IV a YBCO omwe amawalitsidwa ndi mphamvu zosiyanasiyana za laser. b (pamwamba), Kudalira mphamvu ya laser ya voliyumu yotseguka ya Voc ndi mphamvu yafupifupi ya Isc. Ma Isc values sangapezeke pa mphamvu yotsika ya kuwala (< 110 mW/cm2) chifukwa ma curve a IV ali ofanana ndi I-axis pamene chitsanzo chili mu superconducting state. b (pansi), kukana kosiyana ngati ntchito ya mphamvu ya laser.
Kudalira kwa mphamvu ya laser ya Voc ndi Isc pa 80 K kwawonetsedwa mu Chithunzi 2b (pamwamba). Makhalidwe a photovoltaic akhoza kufotokozedwa m'madera atatu a mphamvu ya kuwala. Dera loyamba lili pakati pa 0 ndi Pc, momwe YBCO ikuwongolera mphamvu, Voc ndi yoipa ndipo imachepa (mtengo wake wonse umawonjezeka) ndi mphamvu ya kuwala ndipo imafika pamlingo wocheperako pa Pc. Dera lachiwiri limachokera ku Pc kupita ku mphamvu ina yofunika kwambiri P0, momwe Voc imawonjezeka pomwe Isc imachepa ndi mphamvu ya kuwala yomwe ikuwonjezeka ndipo zonse zimafika pa zero pa P0. Dera lachitatu lili pamwamba pa P0 mpaka mkhalidwe wabwinobwino wa YBCO utafika. Ngakhale kuti Voc ndi Isc zonse zimasiyana ndi mphamvu ya kuwala mofanana ndi m'dera lachiwiri, zimakhala ndi polarity yosiyana kuposa mphamvu yofunika kwambiri P0. Kufunika kwa P0 kuli m'chakuti palibe mphamvu ya photovoltaic ndipo njira yolekanitsa mphamvu imasintha bwino panthawiyi. Chitsanzo cha YBCO sichimakhala chowongolera mphamvu mumtundu uwu wa mphamvu ya kuwala koma mkhalidwe wabwinobwino sunafikepo.
Mwachionekere, makhalidwe a photovoltaic a dongosololi akugwirizana kwambiri ndi superconductivity ya YBCO ndi kusintha kwake kwa superconducting. Kukana kosiyana, dV/dI, kwa YBCO kwawonetsedwa mu Chithunzi 2b (pansi) ngati ntchito ya mphamvu ya laser. Monga tanenera kale, mphamvu yamagetsi yomangidwa mkati mwa mawonekedwe chifukwa cha mfundo zofalitsa za Cooper pair kuchokera ku superconductor kupita ku chitsulo. Mofanana ndi zomwe zawonedwa pa 50 K, mphamvu ya photovoltaic imakulitsidwa ndi mphamvu ya laser yowonjezereka kuchokera pa 0 kupita ku Pc. Pamene mphamvu ya laser ifika pamtengo woposa pang'ono Pc, curve ya IV imayamba kupendekera ndipo kukana kwa chitsanzo kumayamba kuwonekera, koma polarity ya mphamvu ya interface siinasinthebe. Zotsatira za kusokonezeka kwa kuwala pa superconductivity zafufuzidwa m'dera looneka kapena pafupi ndi IR. Ngakhale njira yoyambira ndikugawa ma Cooper pairs ndikuwononga superconductivity25,26, nthawi zina kusintha kwa superconductivity kumatha kukulitsidwa27,28,29, magawo atsopano a superconductivity amatha kuyambitsidwa30. Kusowa kwa superconductivity pa Pc kungayambitsidwe ndi kusweka kwa awiriwa pogwiritsa ntchito photo-induced. Pa mfundo ya P0, mphamvu yodutsa pa interface imakhala zero, zomwe zikusonyeza kuti mphamvu ya magetsi mbali zonse ziwiri za interface imafika pamlingo womwewo pansi pa mphamvu yapaderayi ya kuwala. Kuwonjezeka kwina kwa mphamvu ya laser kumapangitsa kuti ma Cooper pair ambiri awonongeke ndipo YBCO imasinthidwa pang'onopang'ono kukhala chinthu cha p-type. M'malo mwa ma electron ndi Cooper pair diffusion, mawonekedwe a interface tsopano amatsimikiziridwa ndi ma electron ndi hole diffusion zomwe zimapangitsa kuti polarity field yamagetsi mu interface isinthe ndipo motero Voc yabwino (yerekezerani Chithunzi 1d, h). Pa mphamvu ya laser yapamwamba kwambiri, kukana kosiyana kwa YBCO saturates kukhale kofanana ndi mkhalidwe wabwinobwino ndipo onse Voc ndi Isc nthawi zambiri zimasiyana molingana ndi mphamvu ya laser (Chithunzi 2b). Izi zikuwonetsa kuti kuwala kwa laser pa normal state YBCO sidzasinthanso resistivity yake ndi mawonekedwe a superconductor-metal interface koma kungowonjezera kuchuluka kwa ma electron-hole pair.
Kuti afufuze momwe kutentha kumakhudzira mphamvu za photovoltaic, dongosolo la metal-superconductor linayatsidwa pa cathode ndi laser yabuluu yamphamvu ya 502 mW/cm2. Ma curve a IV omwe amapezeka pa kutentha kosankhidwa pakati pa 50 ndi 300 K aperekedwa mu Chithunzi 3a. Voltage yotseguka ya Voc, current yafupifupi ya Isc ndi kukana kosiyana kumatha kupezeka kuchokera ku ma curve awa a IV ndipo akuwonetsedwa mu Chithunzi 3b. Popanda kuunikira kwa kuwala, ma curve onse a IV omwe amayesedwa pa kutentha kosiyanasiyana amadutsa komwe akuchokera monga momwe amayembekezeredwa (chithunzi cha Chithunzi 3a). Makhalidwe a IV amasintha kwambiri ndi kutentha kowonjezereka pamene dongosololi likuunikiridwa ndi kuwala kwa laser kolimba (502 mW/cm2). Pa kutentha kochepa, ma curve a IV ndi mizere yolunjika yofanana ndi I-axis yokhala ndi ma values oyipa a Voc. Ma curve awa amakwera mmwamba ndi kutentha kowonjezereka ndipo pang'onopang'ono amasanduka mzere wokhala ndi malo otsetsereka opanda zero pa kutentha kofunikira Tcp (Chithunzi 3a (pamwamba)). Zikuwoneka kuti ma curve onse a IV amazungulira mozungulira mfundo mu quadrant yachitatu. Voc imawonjezeka kuchoka pa mtengo woipa kupita pa wabwino pomwe Isc imatsika kuchoka pa mtengo wabwino kupita pa wabwino. Pamwamba pa kutentha koyambirira kwa superconducting transition Tc ya YBCO, curve ya IV imasintha mosiyana ndi kutentha (pansi pa Chithunzi 3a). Choyamba, malo ozungulira a ma curve a IV amasunthira ku quadrant yoyamba. Kachiwiri, Voc imapitirira kuchepa ndipo Isc imawonjezeka ndi kutentha kowonjezereka (pamwamba pa Chithunzi 3b). Kachitatu, kutsetsereka kwa ma curve a IV kumawonjezeka molunjika ndi kutentha komwe kumabweretsa kukana kwa kutentha kwa YBCO (pansi pa Chithunzi 3b).
Kudalira kutentha kwa mawonekedwe a photovoltaic pa dongosolo la YBCO-Ag paste pansi pa kuwala kwa laser kwa 502 mW/cm2.
Malo ozungulira malo a laser ali mozungulira ma electrode a cathode (onani Chithunzi 1i). a, ma curve a IV omwe amapezeka kuyambira 50 mpaka 90 K (pamwamba) ndi kuyambira 100 mpaka 300 K (pansi) ndi kutentha kowonjezereka kwa 5 K ndi 20 K, motsatana. Chigawo cha a chikuwonetsa makhalidwe a IV pa kutentha kosiyanasiyana mumdima. Ma curve onse amadutsa malo oyambira. b, voteji yotseguka ya Voc ndi current yafupifupi ya Isc (pamwamba) ndi kukana kosiyana, dV/dI, ya YBCO (pansi) ngati ntchito ya kutentha. Kutentha kwa zero resistance superconducting transition Tcp sikuperekedwa chifukwa kuli pafupi kwambiri ndi Tc0.
Kutentha kofunikira kutatu kungadziwike kuchokera pa Chithunzi 3b: Tcp, pamwamba pake YBCO si superconducting; Tc0, pomwe Voc ndi Isc zonse zimakhala zero ndi Tc, kutentha koyambirira kosinthira kwa superconducting kwa YBCO popanda laser irradiation. Pansi pa Tcp ~ 55 K, laser irradiated YBCO ili mu superconducting yokhala ndi kuchuluka kwakukulu kwa Cooper pairs. Zotsatira za laser irradiation ndikuchepetsa kutentha kwa zero resistance superconducting transition kuchokera pa 89 K mpaka ~55 K (pansi pa Chithunzi 3b) pochepetsa kuchuluka kwa Cooper pairs kuphatikiza pakupanga photovoltaic voltage ndi current. Kutentha kowonjezereka kumaphwanyanso Cooper pairs zomwe zimapangitsa kuti pakhale mphamvu yotsika mu interface. Chifukwa chake, mtengo wokwanira wa Voc udzakhala wocheperako, ngakhale mphamvu yomweyo ya kuwala kwa laser ikugwiritsidwa ntchito. Interface potential idzakhala yocheperako pang'ono ndi kuwonjezeka kwa kutentha ndikufika pa zero pa Tc0. Palibe photovoltaic effect pamalo apadera awa chifukwa palibe munda wamkati wolekanitsa ma electron-hole pairs omwe amapangidwa ndi photo-induced. Kutembenuka kwa mphamvu ya polarity kumachitika pamwamba pa kutentha kofunikira kumeneku chifukwa kuchuluka kwa mphamvu yaulere mu Ag paste kumakhala kwakukulu kuposa kwa YBCO komwe kumasamutsidwa pang'onopang'ono kukhala chinthu cha mtundu wa p. Apa tikufuna kutsindika kuti kusintha kwa mphamvu ya Voc ndi Isc kumachitika nthawi yomweyo pambuyo pa kusintha kwa zero resistance superconducting, mosasamala kanthu za chifukwa cha kusinthaku. Kuwona kumeneku kukuwonetsa momveka bwino, koyamba, mgwirizano pakati pa superconductivity ndi zotsatira za photovoltaic zogwirizana ndi mphamvu ya mawonekedwe a metal-superconductor. Mtundu wa mphamvu iyi mu mawonekedwe a superconductor-normal metal wakhala cholinga chofufuza kwa zaka makumi angapo zapitazi koma pali mafunso ambiri omwe akuyembekezera kuyankhidwa. Kuyeza mphamvu ya photovoltaic kungakhale njira yothandiza yofufuzira tsatanetsatane (monga mphamvu yake ndi polarity etc.) ya mphamvu yofunikayi motero kukuwonetsani mphamvu ya superconducting proximity ya kutentha kwambiri.
Kuwonjezeka kwa kutentha kuchokera ku Tc0 kupita ku Tc kumabweretsa kuchuluka kochepa kwa ma Cooper pairs ndi kukulitsa mphamvu ya interface ndipo motero Voc yayikulu. Pa Tc kuchuluka kwa ma Cooper pairs kumakhala zero ndipo mphamvu yomangira mkati mwa interface imafika pamlingo wapamwamba, zomwe zimapangitsa kuti Voc yayikulu ndi Isc yocheperako ifike. Kuwonjezeka mwachangu kwa Voc ndi Isc (mtengo wokwanira) mu kutentha uku kukugwirizana ndi kusintha kwa superconducting komwe kumakulitsidwa kuchokera ku ΔT ~ 3 K mpaka ~ 34 K ndi kuwala kwa laser kwa mphamvu ya 502 mW/cm2 (Chithunzi 3b). Mu zinthu zabwinobwino pamwamba pa Tc, voteji yotseguka ya Voc imachepa ndi kutentha (pamwamba pa Chithunzi 3b), mofanana ndi momwe Voc imagwirira ntchito pa maselo abwinobwino a solar kutengera pn junctions31,32,33. Ngakhale kuti kusintha kwa Voc ndi kutentha (−dVoc/dT), komwe kumadalira kwambiri mphamvu ya laser, ndi kochepa kwambiri kuposa kwa maselo abwinobwino a solar, kutentha kwa Voc kwa YBCO-Ag junction kuli ndi dongosolo lofanana ndi la maselo a solar. Mphamvu yotuluka ya pn junction ya chipangizo chamagetsi cha dzuwa imawonjezeka ndi kutentha komwe kukukwera, zomwe zimapangitsa kuti Voc ichepe pamene kutentha kukukwera. Ma curve a linear IV omwe awonedwa pa dongosolo la Ag-superconductor, choyamba chifukwa cha kuthekera kochepa kwambiri kwa interface komanso chachiwiri kulumikizana kwa ma heterojunction awiriwa, zimapangitsa kuti zikhale zovuta kudziwa mphamvu yotuluka. Komabe, zikuwoneka kuti kudalira kutentha komweko kwa mphamvu yotuluka ndiko komwe kumayambitsa khalidwe la Voc lomwe lawonedwa mu kuyesa kwathu. Malinga ndi tanthauzo lake, Isc ndiye mphamvu yofunikira kuti ipange voltage yoyipa kuti ibwezeretse Voc kotero kuti voltage yonse ikhale zero. Pamene kutentha kukukwera, Voc imakhala yocheperako kotero kuti mphamvu yochepa ikufunika kuti ipange voltage yoyipa. Kuphatikiza apo, kukana kwa YBCO kumawonjezeka motsatizana ndi kutentha pamwamba pa Tc (pansi pa Chithunzi 3b), zomwe zimathandizanso kuti Isc ikhale yochepa kwambiri pa kutentha kwakukulu.
Onani kuti zotsatira zomwe zaperekedwa mu Zithunzi 2,3 zimapezeka powunikira ndi laser pamalo ozungulira ma electrode a cathode. Miyeso yabwerezedwanso ndi malo a laser omwe ali pa anode ndipo makhalidwe ofanana a IV ndi mawonekedwe a photovoltaic awonedwa kupatula kuti polarity ya Voc ndi Isc yasinthidwa pankhaniyi. Deta yonseyi imabweretsa njira ya photovoltaic effect, yomwe imagwirizana kwambiri ndi mawonekedwe a superconductor-metal.
Mwachidule, makhalidwe a IV a dongosolo la YBCO-Ag lopaka mphamvu ya laser layesedwa ngati ntchito za kutentha ndi mphamvu ya laser. Mphamvu yodabwitsa ya photovoltaic yawonedwa pa kutentha kuyambira 50 mpaka 300 K. Zapezeka kuti mphamvu za photovoltaic zimagwirizana kwambiri ndi superconductivity ya ceramics za YBCO. Kutembenuka kwa polarity kwa Voc ndi Isc kumachitika nthawi yomweyo pambuyo pa kusintha kwa photo-induced superconducting kupita ku kusintha kosasintha kwa superconducting. Kudalira kutentha kwa Voc ndi Isc komwe kumayesedwa pa mphamvu yokhazikika ya laser kumasonyezanso kusintha kwa polarity kosiyana pa kutentha kofunikira pamwamba pomwe chitsanzocho chimakhala chotsutsa. Mwa kupeza malo a laser ku gawo losiyana la chitsanzo, timasonyeza kuti pali mphamvu yamagetsi kudutsa mawonekedwe, zomwe zimapereka mphamvu yolekanitsa mawiri a electron-hole omwe amapangidwa ndi photo-induced. Mphamvu iyi ya interface imatsogolera kuchokera ku YBCO kupita ku electrode yachitsulo pamene YBCO ikupanga superconducting ndipo imasinthira mbali ina pamene chitsanzocho sichikupanga superconducting. Chiyambi cha mphamvuyi chingakhale chogwirizana mwachibadwa ndi zotsatira za kuyandikira kwa magetsi pa mawonekedwe a zitsulo-superconductor pamene YBCO ikupanga mphamvu yamagetsi ndipo akuti ndi ~10−8 mV pa 50 K ndi mphamvu ya laser ya 502 mW/cm2. Kukhudzana kwa chinthu cha mtundu wa p YBCO pamlingo wabwinobwino ndi chinthu cha mtundu wa n. Ag-paste imapanga malo olumikizirana a quasi-pn omwe amachititsa kuti magetsi a YBCO azigwira ntchito pa kutentha kwambiri. Zomwe zawonedwa pamwambapa zikuwonetsa zotsatira za PV mu magetsi a YBCO omwe amagwiritsa ntchito kutentha kwambiri ndipo zimatsegula njira yopezera mapulogalamu atsopano muzipangizo zamagetsi monga chowunikira kuwala mwachangu komanso chowunikira cha photon chimodzi.
Kuyesa kwa mphamvu ya photovoltaic kunachitika pa chitsanzo cha YBCO ceramic cha makulidwe a 0.52 mm ndi mawonekedwe a rectangle a 8.64 × 2.26 mm2 ndipo kunawunikiridwa ndi continuous wave blue-laser (λ = 450 nm) ndi kukula kwa malo a laser a 1.25 mm mu radius. Kugwiritsa ntchito chitsanzo cha bulk m'malo mwa filimu yopyapyala kumatithandiza kuphunzira za mphamvu ya photovoltaic ya superconductor popanda kuthana ndi zovuta za substrate6,7. Kuphatikiza apo, zinthu zambiri zitha kukhala zothandiza pakukonzekera kwake kosavuta komanso mtengo wotsika. Mawaya amkuwa amalumikizidwa pa chitsanzo cha YBCO ndi siliva wopangira ma electrode anayi ozungulira pafupifupi 1 mm m'mimba mwake. Mtunda pakati pa ma electrode awiri a voltage ndi pafupifupi 5 mm. Makhalidwe a IV a chitsanzocho adayesedwa pogwiritsa ntchito magnetometer ya chitsanzo cha vibration (VersaLab, Quantum Design) yokhala ndi zenera la quartz crystal. Njira yokhazikika ya waya zinayi idagwiritsidwa ntchito kuti mupeze ma IV curve. Malo ogwirizana a ma electrode ndi malo a laser akuwonetsedwa mu Chithunzi 1i.
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Ntchitoyi yathandizidwa ndi National Natural Science Foundation of China (Grant No. 60571063), Mapulojekiti Ofufuza Oyambirira a Chigawo cha Henan, China (Grant No. 122300410231).
FY analemba zomwe zinali mu pepalalo ndipo MYH anakonza chitsanzo cha YBCO ceramic. FY ndi MYH anachita kafukufukuyu ndikuwunika zotsatira zake. FGC inatsogolera polojekitiyi ndi kutanthauzira kwasayansi kwa detayo. Olemba onse anawunikanso zolembazo.
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Yang, F., Han, M. & Chang, F. Chiyambi cha mphamvu ya photovoltaic mu superconducting YBa2Cu3O6.96 ceramics. Sci Rep 5, 11504 (2015). https://doi.org/10.1038/srep11504
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