Wurtzite zinc-based oxynitrides as promising photovoltaic absorbers: epitaxy, band-structure engineering and heterostructures

该项目旨在克服薄膜太阳能电池的根本问题，如电池转换效率低以及使用无毒材料的技术障碍。为了实现这一目标，我们将通过将氧化锌与氮化物(AlN，GaN，InN)进行合金化，开发出一类新型的纤锌矿结构非传统半导体材料。这种锌基氮氧化物薄膜的带隙工程可以通过调节价带边和/或导带边来实现。阴离子(O位上的N)和阳离子(Al、Ga和In上的锌位)的取代使能带结构可控，同时保证了结晶度。作为概念证明，我们可以将ZnO-GaN的带隙降低到远低于单一化合物的值。因此，带隙将被调制到可见光或近红外区(接近1.3 eV)，以便有效地收集太阳光。预期的目标是解决用于光伏应用的锌基材料在外延生长和能带结构工程中的关键问题。

This project aims to overcome the fundamental problems of thin film solar cells, such as low cell conversion efficiency as well as technical barriers for the use of non-toxic materials. For this purpose, a new class of unconventional semiconductors with wurtzite structure will be developed by alloying ZnO with III-nitrides (AlN, GaN, InN). Bandgap engineering of such Zn-based oxynitride thin films is achievable by modulating the valence and/or conduction band edges. The substitution of both anion (N on O-site) and cation (Al, Ga and In on Zn-site) allows controllable band structures while ensuring crystallinity. As proof of concept we could reduce the bandgap of ZnO-GaN much below the values of the single compounds. The bandgap would be thereby modulated into the visible light or near-infrared regions (near 1.3 eV) for effective solar-light harvesting. The anticipated goal is tackling the critical problems of Zn-based materials in epitaxial growth and band-structure engineering for photovoltaic application.