Integrated Morphology, Interfacial, and Device Engineering towards High-Performance Perovskite Solar Cells

Thesis (Ph.D.)--University of Washington, 2017-09As a promising renewable energy technology, perovskite solar cells (PVSCs) have made a tremendous progress and received significant attention in recent years, due to the low-cost solution process fabrication, superior charge carrier transporting ability, and decent device performance. In this dissertation, the device performance of PVSCs is enhanced through integrated approaches, such like perovskite thin-film morphology engineering, interface modification of the contact between perovskite and fullerene derivatives layers, and new device architectures. Chapter 1 and 2 briefly overview the current status and the operation mechanism of PVSCs. Chapter 3 demonstrates the importance of the perovskite morphology to the PVSCs performance and the approach of fabricating homogeneous perovskite film. By incorporating Cl- anions, the morphology for both pure I and mixed I-Br perovskite become continuous, resulting in an improved device performance. In chapter 4, another methodology to manipulate the perovskite morphology and crystallinity is proposed. An additive, DIO (1, 8-Diiodooctane), was carefully chosen to manipulate the perovskite morphology due to its capability to chelate Pb2+ cations. As a result, the increase of precursor solubility and the change of the perovskite crystal growth path generate high-quality perovskite film and decent device performance. Chapter 5 presents an interface charge redistribution between the perovskite active layer and fullerene derivatives, like C60, PCBM, and ICBA. This interesting finding gives us a deeper understating when we try to choose a suitable charge transporting material for high-performance PVSCs. In chapter 6, a device fabrication process is employed to enhance the charge collection efficiency for fullerene layer and passivate the defect states at low bandgap perovskite surface and boundary