(6gl) Continuous Manufacturing of Ultrathin Electronic/Optoelectronic Devices with Colloidal Nanocrystals

The pervasiveness of electronic devices in our everyday life is increasing, heading towards a ubiquitous environment involving cutting-edge technology in fields of artificial intelligence, the “Internet of Things,” autonomous vehicles, etc. In particular, wireless communication between the human body and objects is an emerging multi-disciplinary field that finds numerous applications from many diverse research areas. Merging electronic devices with our human body can be realized through the development of wearable/implantable ultrathin electronic devices which conform to the soft human tissues. It is expected that the wearable/implantable technology will lead to electronic skin displays, real-time health monitoring systems, brain-computer interfaces, and many others. Colloidal semiconductor nanocrystals have drawn considerable interest as attractive building blocks for flexible and printable electronic/optoelectronic devices. A critical barrier to commercialization, however, is the toxicity associated with usage of heavy metals (e.g. Pb or Cd), which makes RoHS compliant nanocrystals (e.g. CISeS, CZTS, Si, Ge etc.) particularly attractive for potentially biocompatible electronic devices. Hence, understanding the charge carrier transport characteristics of non-toxic semiconductor nanocrystals thin films and their practical application are crucial to their implementation in wearable/implantable electronic/optoelectronic technologies.

I have previously demonstrated the first switchable-logic devices (CMOS inverter, and NAND or NOR gate devices) using engineered non-toxic colloidal semiconductor nanocrystals. To expand on this, starting from the functionalized nanocrystals, I seek to develop ultrathin printable logic-gate and optoelectronic devices on flexible substrate for achieving wearable/implantable electronic devices. This research will involve: 1) synthesis of solution-processed non-toxic semiconductor nanocrystals; 2) exploration of suitable surface ligands for biocompatible electronic devices; and 3) design and fabrication of ultrathin logic-gate and optoelectronic device architectures. In particular, engineering the surface ligands of tailored nanocrystals strongly influences the carrier transport polarity (unipolar p- or n-type, or ambipolar) of electronic devices, which are basic characteristic for fabricating efficient logic-gate devices and other devices such as light-emitting field-effect transistors (FETs). These devices are highly applicable to wearable/implantable ultrathin electronic gadgets. Therefore, understanding the ligand chemistry for non-toxic semiconductor nanocrystals will be crucial for fabricating high-performance electronic/optoelectronic devices. Recently, inorganic ligands such as halide, chalcogenide and metal-chalcogenide complex ions have been extensively used to produce strong electronic coupling between nanocrystals, and tune the transport polarity. My research group will employ various classes of atomic inorganic ligands to non-toxic semiconductor nanocrystals for achieving high performance logic-gate and opto-electronic devices on the ultrathin substrates. The versatile tunability of transport polarity of nanocrystal film with applying various inorganic ligands is expected to enable inexpensive and high-throughput solution-based processing of ultrathin electronic/optoelectronic devices in ambient environment. In particular, this significant simplification of integration processes implies the feasibility of high profile fabrication of various device geometries.

In order to pursue such ambitious lines of research, significant financial resources will be needed. All funding opportunities available to me will be pursued, starting with National Science Foundation (NSF) fellowship applications for all grad students with a reasonable chance of success. In the beginning phases, I will also apply for early career grants such as the ACS PRF Doctoral New Investigator Grant and the NSF Early Career Award. Furthermore, national research foundation of South Korea (my home country) opens the chance to make international collaboration with exceptional research groups. I will tackle the main funding agencies with my previous collaborator in Seoul National University, KAIST, Samsung, and so on.

Teaching Interests:

As a teaching assistant, I helped students at undergraduate courses of Chemical Engineering Experiments and Transport Phenomena in both Ajou University and Seoul National University. In addition, I mentored undergraduate and graduate students in research when I was senior PhD graduate students and post-doctoral associate. I was also invited to give research talks several universities and high school.

I have three important key words as mentoring philosophy. 1) Socratic elenchus. As mentor, I lead a mentee to find their own answer by themselves. For this great endeavor, I asked and got answers to stimulate critical thinking. 2) Open mind. In research society, somebody was really unwilling to show their results because of a fear of being scooped. But I emphasized we are studying to make better world, not to get a fund or good papers. Open mind always makes scientific revolution in various research fields. 3) Beyond the ivory tower. As an engineer, I lead mentee to link our knowledge from text book and our real life. This kind of linkage made the learner feel fun of studying and motivate their creativity.