Development of the solar cells using the ferroelectric semiconductor heterointerface

采用水热法在SrTiO3单晶衬底上制备了BiFeO3外延薄膜。BiFeO3外延膜的电阻太大而不能测量用于确定能带图（导带最小值和价带最大值的能量位置）的紫外光电子能谱，并且太小而不能测量它们。然后，极化钛酸钡被用作测试样品的确认的带斜率引起的极化：清晰的带斜率观察到的XPS测量与低能量的电子淹没枪。因此，在极化铁电太阳能电池中，可以预期开路电压大于带隙能量。

BiFeO3 epitaxial films were prepared by hydrothermal synthesis method on the SrTiO3 single crystalline substrates. The resistance of the BiFeO3 epitaxial films was too large to measure ultraviolet photoelectron spectroscopy for determining the band diagram (the energy positions of the conduction band minimum and the valence band maximum) and too small to polarize them. Then, polarized BaTiO3 was employed as the test sample for the confirmation of the band slope induced by the polarization: clear band slope was observed by XPS measurements with a low-energy electron flood gun. As a result, open-circuit voltage which is larger than the band gap energy can be expected in polarized ferroelectric solar cells.