LAUSR

Light capture and electron recombination are the essential processes that determine power conversion efficiency (PCE) in quantum dot sensitized solar cells (QDSCs). It is well known that charges are easily transported in well-built QDSCs based on nanorod arrays. However, this advantage can be drastically weakened by defects located at the zinc oxide (ZnO) array surface which permit faster electron recombination. Hence, we developed a composite nanostructure consisting of ZnO nanorods coated with orthorhombic configuration titanium dioxide (TiO2) nanoparticles, which were synthesized using a solution of H3BO3 and (NH4)2TiF6. This composite nanostructure was designed to take the advantage of the enlarged surface area provided by the nanoparticles and improved electron transport along the nanorods, in order to yield good charge transport and light harvesting. At the same time, the TiO2/ZnO nanorod arrays have fewer recombination centers (hydroxyl groups) after TiO2 modification, which results in fewer electron trapping events at the ZnO nanorod surface; thereby, a reduced charge recombination and longer electron lifetime can be achieved. As a result, the PCE of the QDSCs with TiO2-nanoparticles-decorated ZnO nanorod arrays photoelectrode reaches 4.8%, which is ~78% higher efficiency compared to 2.7% for solar cells without modification.摘要光捕获和电子复合决定着量子点敏化太阳电池的光电效率(PCE). 众所周知, 在纳米棒阵列的量子点敏化太阳电池中电荷更容易传 输. 然而, 氧化锌(ZnO)阵列表面的缺陷会引起电荷快速复合. 因此, 我们利用H3BO3和(NH4)2TiF6溶液合成了正交结构的二氧化钛(TiO2)纳 米粒子并用其对ZnO纳米棒包覆, 形成了复合纳米结构. 该结构利用了纳米颗粒提供的大比表面积以及纳米棒优良的电子传输特性, 以期 获得良好的电荷传输和光捕获能力. 同时, 由于TiO2修饰后的ZnO纳米棒阵列的表面复合中心(羟基)较少, ZnO纳米棒表面上发生的电荷俘 获减少, 从而降低了电荷复合, 延长了电子寿命. TiO2修饰后太阳电池的PCE达到4.80%, 比未修饰电池的PCE(2.7%)提高了约78%.