Perylene Diimide as an Electron Transport Material in Optoelectronics
Date
2021-01-12
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0002-4344-4459
Type
Thesis
Degree Level
Doctoral
Abstract
Solar cells and X-ray detectors are important components of commercial power generation and medical imaging, respectively. These devices rely on the generation of charge carriers in a semiconductor when light is absorbed and the subsequent extraction of those charges. The development of new semiconductors could lead to improved charge carrier extraction in solar cells and contrast in X-ray detectors. This thesis is focused on the design of new organic materials to improve the efficiency of organic solar cells and the design of solution processed X-ray detectors to improve the performance of these devices.
This thesis describes the design of perylene diimide electron acceptors for organic solar cells and describes the first use of slot-die coating to deposit methylammonium lead iodide to fabricate X-ray detectors. In the first section I focus on the design, synthesis, and characterization of a nitrile-substituted perylene diimide dimer. The focus of this work is the disruption of intermolecular π-π stacking interactions through dimerization, while simultaneously lowering the energy of the lowest unoccupied molecular orbital by introducing nitrile groups. Solar cell performance is improved by pairing high electron affinity donors with these acceptors, but reduced when a donor with a lower electron affinity is employed.
The second section is focused on the slot-die coating and characterization of methylammonium lead iodide films capable of absorbing 30 kVp X-rays. These can be improved using a slot-die coated perylene diimide hole blocking layer and poly(methyl methacrylate) encapsulation layer. The hole blocking layer reduces the dark current and the poly(methyl methacrylate) encapsulation layer protects the devices from ambient moisture. These devices are compared to state-of-the-art amorphous selenium devices and exhibit significantly lower dark currents. Air ionization was identified as an additional source of photocurrent, which presents challenges in device characterization.
This thesis shows the utility of perylene diimide semiconductors in optoelectronic devices. Here I describe the development of regioisomerically pure 1,7-dicyano perylene diimide semiconductors and the use of a slot-die coater to prepare 100 µm thick methylammonium lead iodide films.
Description
Keywords
Chemistry, Optoelectronics, Renewables, Health Care, Solar Cells, X-Ray Detectors
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Chemistry
Program
Chemistry