Photovoltaic effect in YBa2Cu3O7−δ/Nb-doped SrTiO3 heterojunctions

Abstract

The photovoltaic properties of YBa2Cu3O7−δ/Nb-doped SrTiO3 (SNTO) heterostructures were investigated systematically under laser irradiation of different wavelengths from 365 nm to 640 nm. A clear photovoltaic effect was observed, and the photovoltage Voc ranged from 0.1 V to 0.9 V depending on the wavelength. The Voc appeared under laser illumination with a photon energy of 2.4 eV, far below the band gap (3.2 eV) of Nb-doped SrTiO3. The temperature dependencies of the Voc and short-current density showed kinks near the structural phase transition of the Nb-doped SrTiO3. Our findings are helpful for understanding the photovoltaic effect in transition-metal oxide based heterojunctions and designing such photovoltaic devices.

Photoinduced electronic and ionic effects in strontium titanate

“…While in the temperature regime below 300 K, usually higher photovoltages were found at very low temperatures [181], surprisingly high photovoltages can also be observed at higher temperatures. Brunauer et al demonstrated that La 0.8 Sr 0.2 CrO 3 /STO heterojunctions coupled with a solid oxide fuel cell can be operated at temperatures between 400 and 500 • C with photovoltages close to 1.0 V [23].…”

“…For the LSM/Nb:STO interface, also an insulating interlayer was shown to enhance the photovoltage [162]. [181]. Indeed, the temperature dependence of the photovoltage shows a kink at 100 -120 K. This temperature is attributed to the phase transition from cubic to tetragonal STO [181] and the band gap increases from 3.2 eV at 4.2 K to 3.23 eV near the phase transition and decreases with temperature after the phase transition, thus explaining the kink in the recorded photovoltage curve [181].…”

“…[181]. Indeed, the temperature dependence of the photovoltage shows a kink at 100 -120 K. This temperature is attributed to the phase transition from cubic to tetragonal STO [181] and the band gap increases from 3.2 eV at 4.2 K to 3.23 eV near the phase transition and decreases with temperature after the phase transition, thus explaining the kink in the recorded photovoltage curve [181]. In contrast, the superconducting transition of YBCO at 90 K does not result in any significant feature in the temperature dependence of the photovoltage [181].…”

A High Temperature Harvestorer Based on a Photovoltaic Cell and an Oxygen Ion Battery

“…Room temperature oxide solar cells have been realized based on, e.g., Cu 2 O, ZnO, TiO 2 , or BiFeO 3 . − Also, SrTiO 3 (STO) exhibits a wide range of interactions with light, e.g. photochromism, , photoconductivity, , and photo-oxidation. ,, It forms photoactive heterojunctions with a multitude of materials, for example, Nb:SrTiO 3 /YBa 2 Cu 3 O 7−δ (YBCO), Nb:SrTiO 3 /La 0.5 Ca 0.5 MnO 3−δ , or Nb:SrTiO 3 /Cu 2 O . For our specific high temperature harvestorer it is essential that interfaces between undoped STO single crystals and mixed conductors such as La 0.9 Sr 0.1 CrO 3−δ (LSCr) or La x Sr 1– x MnO 3−δ (LSM) generate very high photovoltages of several hundred mV also at temperatures of about 200 to 400 °C. , …”

Metal Titanate (ATiO3, A: Ni, Co, Mg, Zn) Nanorods for Toluene Photooxidation under LED Illumination

“…Up to this moment, ATiO 3 compounds have been employed for photocatalytic hydrogen production [28][29][30], degradation of toxic aqueous pollutants [30][31][32][33][34][35][36][37], gas sensing [38,39], microwave applications [40], water purification [41], and photovoltaic applications [42][43][44]. In TiO 2 and TiO 2 -related materials the photocatalytic degradation of gaseous pollutants like toluene [45][46][47], nitric oxides NO x [48][49][50], and 2-propanol [51] has been studied.…”