Poly (3-hexylthiophene) (P3HT) thin films were deposited using emulsion-based, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) from emulsions containing different solvents and different alcohols, to investigate the impact of emulsion on film morphology. The atomic force microscopy (AFM) and grazing-incidence, wide angle x-ray scattering (GIWAXS) results show that surface morphology of RIR-MAPLE as-deposited films can be varied from rough to smooth and the microcrystalline domain orientations with respect to the substrate can be tuned from randomly oriented to preferentially oriented in the vertical direction. The demonstrated ability to tune the structural characteristics of polymer thin films by controlling the target emulsion is important for the application of organic optoelectronic devices deposited by RIR-MAPLE.

In this paper we investigate the optical properties of four CdSe colloidal quantum dot/conducting polymer nanocomposites deposited on GaAs substrates using photoluminescence and Fourier transform infrared spectroscopy absorbance. The purpose of this investigation is to find an appropriate electron-conducting polymer for use in a photoconductor that utilizes intraband transitions in the conduction band to detect mid- to long-wave-infrared radiation. As a feasibility demonstration, we fabricate a two-terminal photoconductor and characterize its dark current and spectral responsivity (at 125 K), demonstrating intraband peaks at 0.465 and 0.527 eV, which correspond to 2.67 and 2.35μm.

The motivation and distinct approach for this work is the use of intraband transitions within colloidal quantum dots for the detection of mid- (3-5 μm) and/or long-wave (8-14 μm) infrared light. The CdSe colloidal quantum dot/MEH-PPV conducting polymer nanocomposite material is well-suited for this application due to the ∼1.5 eV difference between the corresponding electron affinities. Therefore, CdSe colloidal quantum dots embedded in MEH-PPV should provide electron quantum confinement such that intraband transitions can occur in the conduction band. Further, it is desirable to deposit these nanocomposites on semiconductor substrates to enable charge transfer of photogenerated electron-hole pairs from the substrate to the nanocomposite. In this way, optoelectronic devices analogous to those achieved using Stranski-Krastanow quantum dots grown by epitaxy can be realized. To date, there have been relatively few investigations of colloidal quantum dot nanocomposites deposited on GaAs substrates. However, it is crucial to develop a better understanding of the optical properties of these hybrid material systems if such heterostructures are to be used for optoelectronic devices, such as infrared photodetectors. By depositing the nanocomposites on GaAs substrates featuring different doping characteristics and measuring the corresponding Fourier transform infrared absorbance, the feasibility of these intraband transitions is demonstrated at room temperature.

Long-wavelength infrared detectors operating at elevated temperatures are critical for imaging applications. InAs/GaAs quantum dots are an important material for the design and fabrication of high-temperature infrared photodetectors. Quantum dot infrared photodetectors allow normal-incidence operation, in addition to low dark currents and multispectral response. The long intersubband relaxation time of electrons in quantum dots improves the responsivity of the detectors, contributing to better hightemperature performance. We have obtained extremely low dark currents (Idark = 1.7 pA, T = 100 K, Vbias = 0.1 V), high detectivities (D* = 2.9×108cmHz1/2/W, T = 100 K, Vbias = 0.2 V), and high operating temperatures (T = 150 K) for these quantum-dot detectors. These results, as well as infrared imaging with QDIPs, will be described and discussed.