Development of the solar cells using the ferroelectric semiconductor heterointerface

采用水热合成法在钛酸锶单晶衬底上制备了BiFeO3外延薄膜。BiFeO_3外延薄膜的电阻太大，无法测量紫外光电子能谱来确定能带图(导带最小和价带最大的能量位置)，也太小，不能对它们进行极化。然后，用极化的BaTiO_3作为测试样品，证实了极化引起的带斜率：用低能电子注入枪进行XPS测量，观察到明显的带斜率。因此，在偏振铁电太阳电池中，开路电压有望大于带隙能量。

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.