2 research outputs found
Energy Gap between Photoluminescence and Electroluminescence as Recombination Indicator in Organic Small-Molecule Photodiodes
Charge transfer (CT)
states at the donor–acceptor interfaces
play an important role in organic optoelectronic devices, yielding
photocarrier generation or recombination losses. In this study, we
fabricate and characterize vacuum-deposited organic photodiodes (OPDs)
composed of SubPc:C60 with various active-layer thicknesses and mixing
ratios in terms of the charge separation efficiency (CSE) and charge
collection efficiency (CCE). We demonstrate that the combined field-assisted
quenching study using both photoluminescence (PL) and electroluminescence
(EL) reveals detailed information on the device physics of bulk heterojunction
photodiodes as related to the CT state. Our modified PL quenching
efficiency approach allows us to reasonably evaluate the CSE. In addition,
we find that the EL energy is closely related to the recombination
loss factor, and the energy gap between PL and EL exhibits a strong
linear relationship with the CCE. As a result, the energy gap is proved
to be a meaningful indicator of the carrier transport properties,
which allows prediction of the CCE in organic bulk heterojunctions
Silent Speech Recognition with Strain Sensors and Deep Learning Analysis of Directional Facial Muscle Movement
Silent communication based on biosignals from facial
muscle requires
accurate detection of its directional movement and thus optimally
positioning minimum numbers of sensors for higher accuracy of speech
recognition with a minimal person-to-person variation. So far, previous
approaches based on electromyogram or pressure sensors are ineffective
in detecting the directional movement of facial muscles. Therefore,
in this study, high-performance strain sensors are used for separately
detecting x- and y-axis strain.
Directional strain distribution data of facial muscle is obtained
by applying three-dimensional digital image correlation. Deep learning
analysis is utilized for identifying optimal positions of directional
strain sensors. The recognition system with four directional strain
sensors conformably attached to the face shows silent vowel recognition
with 85.24% accuracy and even 76.95% for completely nonobserved subjects.
These results show that detection of the directional strain distribution
at the optimal facial points will be the key enabling technology for
highly accurate silent speech recognition