Polymer Based Photodetectors
- PDF / 100,409 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 25 Downloads / 174 Views
I13.5.1
Polymer Based Photodetectors K. S. Narayan, D. Kabra, and S. Dutta Chemistry and Physics of Material Unit Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur, Bangalore, 560064, India
ABSTRACT Recent developments in our laboratory related to polymer-based light sensors are reviewed. The inherent processibility of the active polymer medium is utilized in the implementation of different designs for the opto-electronic applications. The utility of these devices as sensitive photodetectors, image sensors and position sensitive detectors is demonstrated. The schottky-type layer formation at interfaces of polymers such as polyalkylthiophenes and aluminum accompanied by the enhanced photo-induced charge separation due to high local electric field is tapped for some of these device structures. The sensitivity of polymer-based field effect transistors to light also provides a convenient lateral geometry for efficient optical-coupling and control of the transistor state. The range of these polymer-detectors available with the option of operating in the diode and transistor modes should be an attractive feature for many potential applications. INTRODUCTION The use of polymers/organics as active materials for electronics and opto-electronic applications has introduced novel concepts in product-designs. These unconventional designs rely on the processibility of these polymeric materials which can be effectively used in locations, which typically restrict conventional semiconductor devices [1]. Electronic price tags and flexible displays are among the sought-after applications for these systems. Over, the recent years, our laboratory has adopted different strategies to enhance the sensitivity of these polymer based structures. Three distinct approaches have been adopted for this purpose: (i) Intrinsic quantum efficiency for generation of free carriers in the polymer media were improved. In the last decade, efforts to increase the quantum efficiency of charge generation and separation efficiencies in polymers such as derivatives of polyphenylenevinylene (PPV) and polythiophene (PTH) were quite successful by blending or introducing suitable electron acceptors such as nanoparticles of titanium dioxide and Cadmium Sulfide in the polymer matrix [2-4]. Introduction of donor-acceptor interface tremendously increases the photoactivity due to the exciton accumulation at the interface which is followed by an effective charge transfer. Single layer blends as well as multilayer structures of these materials were explored. (ii) Strategies to optimize external geometrical parameters were implemented. The concept of ‘resonance cavity enhanced’ (RCE) photodiodes for inorganic devices was adapted for the polymer-based devices successfully [5]. The procedure entails the introduction of a thin polymer active layer in the micro-cavity, which is essentially a resonator with an effective cavity length of half the wavelength of light. We observe, upon implementing the RCE structure, that the gain of
I13.5.2
the photodiode is n
Data Loading...
