Wu Fan, Qiao Qiquan, Bahrami Behzad, Chen Ke, Pathak Rajesh, Tong Yanhua, Li Xiaoyi, Zhang Tiansheng, Jian Ronghua
School of Science and Key Lab of Optoelectronic Materials and Devices, Huzhou University, Huzhou, Zhejiang Province 313000, People's Republic of China.
Nanotechnology. 2018 May 25;29(21):215403. doi: 10.1088/1361-6528/aab59e. Epub 2018 Mar 9.
We present a method to synthesize CuO nanorod array/TiO nanocrystals bulk heterojunction (BHJ) on fluorine-tin-oxide (FTO) glass, in which single-crystalline p-type semiconductor of the CuO nanorod array is grown on the FTO glass by hydrothermal reaction and the n-type semiconductor of the TiO precursor is filled into the CuO nanorods to form well-organized nano-interpenetrating BHJ after air annealing. The interface charge transfer in CuO nanorod array/TiO heterojunction is studied by Kelvin probe force microscopy (KPFM). KPFM results demonstrate that the CuO nanorod array/TiO heterojunction can realize the transfer of photo-generated electrons from the CuO nanorod array to TiO. In this work, a solar cell with the structure FTO/CuO nanoarray/TiO/Al is successfully fabricated, which exhibits an open-circuit voltage (V ) of 0.20 V and short-circuit current density (J ) of 0.026 mA cm under AM 1.5 illumination. KPFM studies indicate that the very low performance is caused by an undesirable interface charge transfer. The interfacial surface potential (SP) shows that the electron concentration in the CuO nanorod array changes considerably after illumination due to increased photo-generated electrons, but the change in the electron concentration in TiO is much less than in CuO, which indicates that the injection efficiency of the photo-generated electrons from CuO to TiO is not satisfactory, resulting in an undesirable J in the solar cell. The interface photovoltage from the KPFM measurement shows that the low V results from the small interfacial SP difference between CuO and TiO because the low injected electron concentration cannot raise the Fermi level significantly in TiO. This conclusion agrees with the measured work function results under illumination. Hence, improvement of the interfacial electron injection is primary for the CuO nanorod array/TiO heterojunction solar cells.
我们提出了一种在氟掺杂氧化锡（FTO）玻璃上合成氧化铜纳米棒阵列/二氧化钛纳米晶体体相异质结（BHJ）的方法，其中通过水热反应在FTO玻璃上生长出单晶p型半导体氧化铜纳米棒阵列，然后将二氧化钛前驱体的n型半导体填充到氧化铜纳米棒中，经过空气退火后形成组织良好的纳米互穿BHJ。通过开尔文探针力显微镜（KPFM）研究了氧化铜纳米棒阵列/二氧化钛异质结中的界面电荷转移。KPFM结果表明，氧化铜纳米棒阵列/二氧化钛异质结能够实现光生电子从氧化铜纳米棒阵列向二氧化钛的转移。在这项工作中，成功制备了结构为FTO/氧化铜纳米阵列/二氧化钛/铝的太阳能电池，在AM 1.5光照下，其开路电压（V）为0.20 V，短路电流密度（J）为0.026 mA/cm²。KPFM研究表明，这种极低的性能是由不理想的界面电荷转移导致的。界面表面电位（SP）显示，光照后氧化铜纳米棒阵列中的电子浓度由于光生电子的增加而发生了显著变化，但二氧化钛中电子浓度的变化远小于氧化铜中的变化，这表明光生电子从氧化铜注入到二氧化钛的效率不令人满意，导致太阳能电池中的J不理想。KPFM测量得到的界面光电压表明，低V是由于氧化铜和二氧化钛之间的界面SP差异较小，因为低注入电子浓度无法显著提高二氧化钛中的费米能级。这一结论与光照下测量的功函数结果一致。因此，改善界面电子注入是氧化铜纳米棒阵列/二氧化钛异质结太阳能电池的首要任务。
