He Xing, Iwamoto Yuta, Kaneko Toshiro, Kato Toshiaki
Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan.
Sci Rep. 2022 Jul 4;12(1):11315. doi: 10.1038/s41598-022-15352-x.
Herein, we developed a near-invisible solar cell through a precise control of the contact barrier between an indium tin oxide (ITO) electrode and a monolayer tungsten disulfide (WS), grown by chemical vapor deposition (CVD). The contact barrier between WS and ITO was controlled by coating various thin metals on top of ITO (M/ITO) and inserting a thin layer of WO between M/ITO and the monolayer WS, which resulted in a drastic increase in the Schottky barrier height (up to 220 meV); this could increase the efficiency of the charge carrier separation in our Schottky-type solar cell. The power conversion efficiency (PCE) of the solar cell with the optimized electrode (WO/M/ITO) was more than 1000 times that of a device using a normal ITO electrode. Large-scale fabrication of the solar cell was also investigated, which revealed that a simple size expansion with large WS crystals and parallel long electrodes could not improve the total power (P) obtained from the complete device even with an increase in the device area; this can be explained by the percolation theory. This problem was addressed by reducing the aspect ratio (width/channel length) of the unit device structure to a value lower than a critical threshold. By repeating the experiments on this optimized unit device with an appropriate number of series and parallel connections, P could be increased up to 420 pW from a 1-cm solar cell with a very high value (79%) of average visible transmission (AVT).
在此，我们通过精确控制铟锡氧化物（ITO）电极与通过化学气相沉积（CVD）生长的单层二硫化钨（WS）之间的接触势垒，开发了一种近乎隐形的太阳能电池。WS与ITO之间的接触势垒通过在ITO顶部涂覆各种薄金属（M/ITO）并在M/ITO与单层WS之间插入一层薄的WO来控制，这导致肖特基势垒高度大幅增加（高达220毫电子伏特）；这可以提高我们肖特基型太阳能电池中电荷载流子分离的效率。具有优化电极（WO/M/ITO）的太阳能电池的功率转换效率（PCE）比使用普通ITO电极的器件高出1000倍以上。我们还研究了太阳能电池的大规模制造，结果表明，即使增加器件面积，使用大尺寸WS晶体和平行长电极进行简单的尺寸扩展也无法提高整个器件获得的总功率（P）；这可以用渗流理论来解释。通过将单元器件结构的纵横比（宽度/沟道长度）降低到低于临界阈值的值来解决这个问题。通过对这种优化的单元器件进行适当数量的串联和并联连接重复实验，从具有非常高的平均可见光透射率（AVT）值（79%）的1厘米太阳能电池中，P可以提高到420皮瓦。
