Photonic data storage
has diverse optoelectronic applications such as optical sensing and
recording, integrated image circuits, and multibit-storage flash memory.
In this study, we employ conjugated/insulated polymer blends as the
charge storage electret for photonic field-effect transistor memory
devices by exploring the blend composition, energy level alignment,
and morphology on the memory characteristics. The studied conjugated
polymers included poly(9,9-di-n-octylfluorenyl-2,7-diyl)
(PF), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV),
poly[{2,5-di(3′,7′-dimethyloctyloxy)-1,4-phenylene-vinylene}-co-{3-(4′-(3″,7″-dimethyloctyloxy)phenyl)-1,4-phenylenevinylene}-co-{3-(3′-(3′,7′-dimethyloctyloxy)phenyl)-1,4-phenylenevinylene}]
(SY-PPV), and poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT), and the insulated
polymers were polystyrene (PS) and poly(methyl methacrylate) (PMMA).
The photonic memory device using the PF/PS blend electret exhibited
a dynamic switching behavior with light-writing and voltage-erasing
processes both within only 1 s, along with a high contrast on the
current on/off ratio between “Photo-On” and “Electrical-OFF”
over 106 and the decent retention time for more than 3
months. In addition, the multilevel memory behavior could be observed
using different light sources of 405, 450, and 520 nm or energy intensity,
which was supported by surface potential analysis. The characteristics
were superior to those of the devices using PF/PMMA blend due to the
higher charge storage behavior of PS supported by fluorescence analysis.
The PF/PS blend film prepared from the chlorobenzene solvent exhibited
mesh-like and aggregated PF domains in the PS matrix and enhanced
the contact surface area between the semiconductor and blend electret,
leading to a higher memory window. The photonic memory behavior was
also observed in the blend electrets of PS with the low band gap polymer,
MEH-PPV, SY-PPV, or F8BT, by changing the photoresponsive light sources.
Our study demonstrated a new electret system to apply on the multilevel
photonic memory devices.