Florida Solar Energy Center , University of Central Florida , Cocoa , Florida 32922 , United States.
Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States.
ACS Appl Mater Interfaces. 2019 Nov 20;11(46):43075-43080. doi: 10.1021/acsami.9b12703. Epub 2019 Nov 7.
In this study, substochiometric hole-selective molybdenum oxide (MoO) contacts in crystalline silicon (c-Si) solar cells were investigated by a combination of transmission electron microscopy (TEM) and spatially resolved electron energy-loss spectroscopy (SR-EELS). It was observed that ≈ 4 nm SiO interlayer grows at the MoO/c-Si interface during the evaporation of MoO over a c-Si substrate. SR-EELS analyses revealed the presence of a 1.5 nm diffused MoO/indium tin oxide (ITO) interface in both as-deposited and annealed samples. Moreover, the presence of a 1 nm thin layer with a lower oxidation state of Mo was detected at the SiO/MoO interface in an as-deposited state, which disappears upon annealing. Overall, it was evident that no hole-blocking interlayer is formed at the MoO/ITO interface during annealing and homogenization of the MoO layer takes place during the annealing process. Furthermore, device simulations revealed that efficient hole collection is dependent on MoO work function and that reduction in the work function of MoO results in loss of band bending and negatively impacts hole selectivity.
在这项研究中，通过透射电子显微镜（TEM）和空间分辨电子能量损失谱（SR-EELS）的组合，研究了晶态硅（c-Si）太阳能电池中亚化学计量空穴选择性氧化钼（MoO）接触。研究发现，在 MoO 蒸发在 c-Si 衬底上时，在 MoO/c-Si 界面处生长了 ≈4nm 的 SiO 层。SR-EELS 分析表明，在沉积态和退火样品中都存在 1.5nm 扩散的 MoO/氧化铟锡（ITO）界面。此外，在沉积态下，在 SiO/MoO 界面处检测到存在 1nm 厚的 Mo 氧化态较低的薄层，该层在退火后消失。总体而言，显然在退火过程中，在 MoO/ITO 界面上没有形成空穴阻挡层，并且在退火过程中，MoO 层均匀化。此外，器件模拟表明，有效的空穴收集依赖于 MoO 的功函数，并且 MoO 的功函数降低会导致能带弯曲损失，并对空穴选择性产生负面影响。
