Title:  High-Performance Organic Photodiodes and Their Applications

Committee: 

Dr. Kippelen, Advisor  

Dr. Chang, Chair

Dr. Inan

Abstract:

The objective of the proposed research is to develop high-performance organic photodiodes (OPDs) for light sensing. OPDs can be fabricated into devices with a flexible form factor using coating and printing techniques that are scalable and therefore that enable large area devices and arrays. Our work establishes that OPDs can yield unprecedented detectivity values that are comparable to those of low-noise inorganic counterparts but at lower voltage and with room temperature operation. In the preliminary research, we discuss the origin of the dark current and select a proper material combination that yields low-noise photodiodes. The optimized OPDs exhibit low dark current density values comparable to those of state-of-the-art Si photodiodes at low voltages. Without adding more complexities in the fabrication, we demonstrate large-area OPDs on plastic substrates with limited dark current values leading to a high detectivity value (1014 Jones), which outperforms rigid Si counterparts with similar size. Flexible and large-area OPDs are fabricated with a novel geometry to record photoplethysmograms (PPG) for applications in physiological sensing. Their highly conformal form factors combined with the new geometry provide improved optical power collection compared to conventional small area Si-based detectors. To develop a universal method for lowering the dark current, we propose to use a tunneling layer grown by atomic layer deposition to passivate defects in OPDs in future work.