The Woodruff School

SUMMARY

Organic electronic devices are attractive for their potential to produce lightweight, scalable, and flexible electronics as opposed to traditional inorganic electronics. In spite of these advantageous properties, the implementation of organic electronics in many applications is still challenging because of the potential for rapid degradation upon environmental exposure to oxygen, humidity, and mechanical stress. To enhance the stability of the devices, a reliable barrier layer to prevent the ingress of moisture and oxygen is required as well as more stable functional layers inside the device. Both of these goals can be partially achieved using defect-free conformal plasma-enhanced atomic layer deposition (PEALD) films integrated into the devices. However, the practical electrical performance as well as the chemical stabilities of ultra-thin PEALD films has not received much attention from researchers. In some cases, characterization methods for the ultra-thin PEALD films have not been established either. Therefore, this dissertation work proposes to investigate the functional properties of ultra-thin (<10 nm) PEALD films to create an encapsulation barrier film as well as to create environmentally robust coatings for electron selective contacts in organic electronics to improve their reliability. First, the chemical stability of PEALD in aqueous environments was evaluated. Based on the results, select PEALD films were applied for the application of either electron selective functional layers in an organic solar cell or robust encapsulation barrier layers for organic solar cells. In addition, the gas barrier performance of ultrathin PEALD films was investigated using an improved calcium corrosion test, which can discriminate between the intrinsic film permeation and the defect-assisted permeation. Also, defect and crack issues observed in the fabrication process of ultrathin thin films are discussed, and a method to avoid the issues is suggested. The results of this research will contribute to the establishment of chemical, electrical, and permeation characterization methods to evaluate the ultra-thin PEALD film as well as to the enhancement of the stability of organic electronic devices.

SUBJECT:	Ph.D. Dissertation Defense

BY:	Hyung Chul Kim

TIME:	Tuesday, August 11, 2015, 10:00 a.m.

PLACE:	MRDC Building, 4211

TITLE:	Investigation of ALD Thin Films to Improve the Reliability of Organic Electronic Devices

COMMITTEE:	Dr. Samuel Graham, Chair (ME) Dr. Ting Zhu (ME) Dr. Shannon Yee (ME) Dr. John R. Reynolds (Chem. & MSE) Dr. Elsa Reichmanis (ChBE)

SUMMARY Organic electronic devices are attractive for their potential to produce lightweight, scalable, and flexible electronics as opposed to traditional inorganic electronics. In spite of these advantageous properties, the implementation of organic electronics in many applications is still challenging because of the potential for rapid degradation upon environmental exposure to oxygen, humidity, and mechanical stress. To enhance the stability of the devices, a reliable barrier layer to prevent the ingress of moisture and oxygen is required as well as more stable functional layers inside the device. Both of these goals can be partially achieved using defect-free conformal plasma-enhanced atomic layer deposition (PEALD) films integrated into the devices. However, the practical electrical performance as well as the chemical stabilities of ultra-thin PEALD films has not received much attention from researchers. In some cases, characterization methods for the ultra-thin PEALD films have not been established either. Therefore, this dissertation work proposes to investigate the functional properties of ultra-thin (<10 nm) PEALD films to create an encapsulation barrier film as well as to create environmentally robust coatings for electron selective contacts in organic electronics to improve their reliability. First, the chemical stability of PEALD in aqueous environments was evaluated. Based on the results, select PEALD films were applied for the application of either electron selective functional layers in an organic solar cell or robust encapsulation barrier layers for organic solar cells. In addition, the gas barrier performance of ultrathin PEALD films was investigated using an improved calcium corrosion test, which can discriminate between the intrinsic film permeation and the defect-assisted permeation. Also, defect and crack issues observed in the fabrication process of ultrathin thin films are discussed, and a method to avoid the issues is suggested. The results of this research will contribute to the establishment of chemical, electrical, and permeation characterization methods to evaluate the ultra-thin PEALD film as well as to the enhancement of the stability of organic electronic devices.