INS10-1629
Understanding Gas Sensing through Multiscale Simulations of Impurity-Modulated Charge Transport
Topic
S10. AI-assisted Design and Simulation of Polymers
When and Where
Sep 29, 2026
15:50 - 16:15
Room 109
Session Chairs
Lisa HALL
Presenter(s)
Kun Han Lin (Department of Chemical Engineering, National Tsing Hua University)
Co-Author(s)
Abstract
Organic semiconductor gas sensors are promising for agriculture, environmental monitoring, and medical diagnostics because they enable low-power, room-temperature operation on low-cost and mechanically flexible platforms. However, the molecular mechanism by which adsorbed gas molecules perturb charge transport remains unclear. Here, using the boron-containing organic semiconductor CzDBA as a model system, we employ multiscale simulations to distinguish the effects of physically adsorbed NH3 from chemically adsorbed NH3 formed through Lewis acid–base interactions with the boron centers, and determine which adsorption mechanism can effectively modulate charge-carrier mobility and produce an NH3 sensing response.
Our framework combines density functional theory, molecular dynamics, and kinetic Monte Carlo simulations within a hopping-transport model. We find that the two adsorption modes have fundamentally different effects on hole transport. Chemisorption of NH3 at the Lewis-acidic boron center shifts the hole site energy of the NH3–CzDBA complex relative to pristine CzDBA, generating shallow trapping sites that transiently localize holes and slow their transport. Consequently, the hole mobility decreases systematically with increasing concentration of chemisorbed NH3, providing a direct microscopic mechanism for the experimentally observed reduction in current upon NH3 exposure. In contrast, physically adsorbed NH3 generates strongly perturbed sites that are energetically unfavorable for hole occupation and therefore do not act as effective hole traps. At the low NH₃ concentrations relevant to sensing experiments (<1%), varying the amount of physically adsorbed NH3 produces no clear systematic change in hole mobility.
These results identify Lewis acid–base chemisorption, rather than physical adsorption, as an effective mechanism for translating NH3 binding into a measurable charge-transport response. More broadly, the study demonstrates how specific molecular interactions can be engineered to create shallow transport traps, providing a mechanistic design principle for highly sensitive organic NH3 sensors and other chemically responsive semiconductor materials.
Our framework combines density functional theory, molecular dynamics, and kinetic Monte Carlo simulations within a hopping-transport model. We find that the two adsorption modes have fundamentally different effects on hole transport. Chemisorption of NH3 at the Lewis-acidic boron center shifts the hole site energy of the NH3–CzDBA complex relative to pristine CzDBA, generating shallow trapping sites that transiently localize holes and slow their transport. Consequently, the hole mobility decreases systematically with increasing concentration of chemisorbed NH3, providing a direct microscopic mechanism for the experimentally observed reduction in current upon NH3 exposure. In contrast, physically adsorbed NH3 generates strongly perturbed sites that are energetically unfavorable for hole occupation and therefore do not act as effective hole traps. At the low NH₃ concentrations relevant to sensing experiments (<1%), varying the amount of physically adsorbed NH3 produces no clear systematic change in hole mobility.
These results identify Lewis acid–base chemisorption, rather than physical adsorption, as an effective mechanism for translating NH3 binding into a measurable charge-transport response. More broadly, the study demonstrates how specific molecular interactions can be engineered to create shallow transport traps, providing a mechanistic design principle for highly sensitive organic NH3 sensors and other chemically responsive semiconductor materials.
