Department of Materials Science and Engineering and Materials Research Institute, Pennsylvania State University , University Park, Pennsylvania 16802, United States.
Advanced Photon Source, Argonne National Laboratory , Lemont, Illinois 60439, United States.
ACS Appl Mater Interfaces. 2017 Apr 12;9(14):12556-12562. doi: 10.1021/acsami.6b16007. Epub 2017 Apr 3.
Mott insulating oxides and their heterostructures have recently been identified as potential photovoltaic materials with favorable absorption properties and an intrinsic built-in electric field that can efficiently separate excited electron-hole pairs. At the same time, they are predicted to overcome the Shockley-Queisser limit due to strong electron-electron interaction present. Despite these premises a high concentration of defects commonly observed in Mott insulating films acting as recombination centers can derogate the photovoltaic conversion efficiency. With use of the self-regulated growth kinetics in hybrid molecular beam epitaxy, this obstacle can be overcome. High-quality, stoichiometric LaVO films were grown with defect densities of in-gap states up to 2 orders of magnitude lower compared to the films in the literature, and a factor of 3 lower than LaVO bulk single crystals. Photoconductivity measurements revealed a significant photoresponsivity increase as high as tenfold of stoichiometric LaVO films compared to their nonstoichiometric counterparts. This work marks a critical step toward the realization of high-performance Mott insulator solar cells beyond conventional semiconductors.
最近，Mott 绝缘氧化物及其异质结构被确定为具有良好吸收特性和固有内置电场的潜在光伏材料，可有效分离激发的电子-空穴对。同时，由于存在强电子-电子相互作用，预计它们将克服肖克利-奎塞尔限制。尽管存在这些前提条件，但在 Mott 绝缘薄膜中常见的高浓度缺陷会作为复合中心降低光伏转换效率。通过在混合分子束外延中使用自调节生长动力学，可以克服这一障碍。与文献中的薄膜相比，高质量、化学计量比的 LaVO 薄膜的间隙态缺陷密度低了 2 个数量级，比 LaVO 体单晶低了 3 倍。光电导测量显示，与非化学计量比的 LaVO 薄膜相比，化学计量比的 LaVO 薄膜的光电响应性显著提高了 10 倍。这项工作标志着朝着实现超越传统半导体的高性能 Mott 绝缘太阳能电池迈出了关键一步。
