High-Capacity, Fast-Response, and Photocapacitor-Based Terpolymer Phosphor Composite

Abstract

This paper describes a new class of light transducer-based poly (vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) terpolymer doped with 50% wt. phosphor particles that enables to efficiently transform light energy into an electrical signal. Broadband dielectric characterization together with experimental results on photo-electric conversion demonstrated high capacitance variation of the proposed composite under light exposure, confirming promising potential of our sensor device for application in retinal prostheses where the converted electrical signal can affect the biological activity of the neuron system. In addition to the benefit of being light-weight, having ultra-flexibility, and used in a simple process, the proposed photodetector composite leads to fast response and high sensibility in terms of photoelectrical coupling where significant increases in capacitance change of 78% and 25% have been recorded under blue and green light sources, respectively. These results demonstrated high-performance material design where phosphor filler contributes to promote charge-discharge efficiency as well as reduced dielectric loss in P(VDF-TrFE-CTFE), which facilitate the composite for flexible light transducer applications, especially in the medical environment.

Keywords: artificial retinal prosthetic device; light sensor; phosphor/terpolymer composite; photocapacitive detector; photoelectrical conversion.

Figure 1

Structure of a flexible terpolymer/phosphor composite.

Figure 2

Experimental setup for photo-capacitor characterization of the polymer composite.

Figure 3

Frequency dependence at various LED lights of (a) the real part of complex permittivity and (b) the dissipation factor.

Figure 4

(a) Capacitance of polymer composite excited by blue and green lights with on/off cycles. (b) Capacitance change (ΔC/C₀) under different wavelength exposure, where ΔC = C − C₀; C and C₀ are, respectively, the capacitance value of the composite with and without light application.

Figure 5

(a) Capacitance change versus light intensity with: (a) blue and green LEDs and, (b) only blue LED with different thicknesses of polymer composites.

Figure 6

Charge–discharge behavior of terpolymer phosphor composite excited under blue and green LEDs.

Figure 7

Photocurrent at various frequencies: (a) 0.3 Hz, (b) 4 Hz, Inset: charge displacement versus time.

Figure 8

Flexible photodetector arrays, consisting of Indium Tin Oxide (ITO)-coated Polyethylene Terephthalate (PET)/polymer composite/Au electrode.

Figure 9

Photo-capacitor arrays using letter-shaped masks.

Figure 10

Schematic illustration corresponding to the capacitance measurement of flexible photocapacitor arrays.