Development of Functional Materials Using Atomic Layer Deposition and Their Applications in Green Energy Technology: Solar Cells, Hydrogen Production via Water Splitting, and Supercapacitors

The development of green energy technologies is a central aim of the world energy policy. However, several hurdles remain in commercialization of state-of-the-art technologies, and the challenges lie in: (1) lack of economical yet high quality functional materials; (2) development of novel device architectures. Atomic layer deposition (ALD), with its unique characteristics of defect-free deposition, excellent step coverage over topographical surface, relative low deposition temperature, excellent conformability and uniformity over large area, is highly suitable for application in green energy technologies. Thus, this project aims to utilize ALD technologies for the development of a variety of novel functional materials, mainly including thin-films and vertically-aligned nanorods. To examine the feasibility of applying ALD technology in perovskite solar cells, hydrogen production using solar radiation-driven water splitting, and supercapacitors, microstructure analysis together with theoretical simulation and device engineering are performed. The objective of this project is to develop promising green energy technologies with the advantages of low-cost, high-performance, highly-stable, and ease of large area production. Our preliminary data has demonstrated the effectiveness of ALD technology, and some significant results have been obtained. In the development of perovskite solar cells, an impressively high power conversion efficiency (PCE) of 16.1% (active area = 0.04 cm2) is obtained when employing ALD NiO and ZnO films as the hole transporting layer and electron transporting layer, respectively. In addition, the PCE still remains high (14.2%) for the large area devices (active area = 6 cm2). Moreover, ALD TiCVAhC^ nanolaminate film, shows excellent gas barrier performance where oxygen transmission rate reaches 9.4><10"3 cm3/m2/day, and water vapor transmission rate reaches 7.7><10_5 g/m2/day. Both of these values meet the requirements for solar cells encapsulation. In the development of supercapacitors, the electrode based on ALD ZnO/NiO core-shell nanorods structure shows a high specific capacitance (1947 F/g) and stable specific capacitance retention after a long cycle test (>1400 cycles). Overall, this project provides fundamental science and optoelectronic device applications. Our results will not only open a new avenue for the development of green energy technologies, but also facilitate the development of advanced electronic devices.