Metal Oxide Interlayers For Solution Processed Optoelectronic Devices

This thesis investigates solution-processed metal oxide charge transport interlayers for optoelectronic devices. We focus on low temperature processed n-type zinc oxide (ZnO) and p-type nickel oxide (NiO) thin films, deposited from either colloidal nanocrystal or so-gel precursor solutions. New materials, novel deposition technology and innovative surface passivation strategy developed in this thesis provide novel thoughts for the application and optimization of the metal oxide-based optoelectronic devices.Primary works involved in this thesis are based on ZnO colloidal nanocrystal films. Based on our understanding on charging nature of ZnO nanocrystal, we developed a room-temperature electrophoretic deposition method to fabricate ZnO nanocrystal films, which were applied to organic electronics field. We introduced a small-molecule modification approach to passivate the surface defects of ZnO films. Upon the covalent bonds formed near surface, various gap states formed by the complex surface groups can be uniformed to a novel efficient electron transport channel. And hence the charge carrier recombination in devices and the sensitivity to oxygen and water of inverted organic solar cells can be further reduced. We find that the band structures of thin films based on ZnO nanocrystals can be efficiently tuned by alloying, which make it possible to customize interlayers for various organic materials used in the optoelectronic devices.For hybrid perovskite solar cells, we investigated the influence of processing conditions on surface morphology, crystalline quality and charge carrier diffusion lengths of the perovskite films. We further modified the cathode interface by integrating a room-temperature deposited ZnO nanocrystal interlayer. Device performance and air stability were significantly improved by optimizing the device structure.Based on zinc-ammonia complex and solution-combustion reactions, we designed new aqueous solutions to fabricate ZnO and NiO thin films at low temperatures, respectively. Surface properties of two kinds of interlayers and their applications in organic optoelectronics were also investigated.