Organic semiconductors (OSCs) have emerged as a new class of electronic materials promising a wide range of applications including organic field-effect transistors (OFET), solar cells, thermoelectrics, electronic skins, and chemical and mechanical sensors by virtue of their chemical versatility, solution processability, and mechanical flexibility.
Controlled fabrication of nanoporous OSCs over a large area can open up a new avenue to tune the (opto)electronic properties, and may even lead to new functions not imagined before, given the wide utility of nanoporous materials for energy storage, chemical separation, catalysis, drug delivery, and beyond. Recent work has demonstrated the fabrication of large-domain porous pentacene thin films by vapor deposition on a small-molecule template.
Solution-coated/printed nanoporous OSCs have not been reported before; the methods demonstrated thus far are not material-agnostic and do not offer wide tunability of pore sizes. Pore structure tunability is particularly important for controlling pore-imparted properties such as sensitivity and response time of OFET-based chemical sensors.
A generic method was developed to fabricate nanoporous thin films, applicable to both polymer and small-molecule OSCs. Nanopores with tunable pore sizes (50-700 nm) were introduced into the semiconductor thin film via simple solution processing methods such as meniscus-guided coating/printing and spin-coating. Nanoporous OFET sensors also were developed for detection of volatile organic compounds (VOCs) such as ammonia and formaldehyde. Sensitive and rapid VOC detection using printed, low-cost sensor chips has potential applications in personalized health and environmental monitoring.
A small, thin square of an organic plastic can detect disease markers in breath, or toxins in a building's air. By riddling the thin plastic films with pores, the devices are sensitive enough to detect at levels that are far too low to smell, yet are important to human health; for example, a device that monitors ammonia in breath could indicate kidney failure. The material is highly reactive to ammonia, but not to other compounds in breath. By changing the composition of the sensor, devices could be created that are tuned to other compounds, such as an ultrasensitive environmental monitor for formaldehyde, a common indoor pollutant in new or refurbished buildings.