Highly sensitive and fast photodetector devices with CdSe quantum nanowires as active elements have been developed exploiting the advantages of electro- and wet-chemical routes. Bismuth nanoparticles electrochemically synthesized directly onto interd
igitating platinum electrodes serve as catalysts in the following solution-liquid-solid synthesis of quantum nanowires directly on immersed substrates under mild conditions at low temperature. This fast and simple preparation process leads to a photodetector device with a film of nanowires of limited thickness bridging the electrode gaps, in which a high fraction of individual nanowires are electrically contacted and can be exposed to light at the same time. The high sensitivity of the photodetector device can be expressed by its on/off-ratio or its photosensitivity of more than 107 over a broad wavelength range up to about 700 nm. The specific detectivity and responsivity are determined to D* = 4*10^13 Jones and R = 0.32 A/W, respectively. The speed of the device reflects itself in a 3 dB frequency above 1 MHz corresponding to rise and fall times below 350 ns. The remarkable combination of a high sensitivity and a fast response is attributed to depletion regions inside the nanowires, tunnel-junction barriers between nanowires, as well as Schottky contacts at the electrodes, where all these features are strongly influenced by the number of photo generated charge carriers.
Thin films prepared of semiconductor nanoparticles are promising for low-cost electronic applications such as transistors and solar cells. One hurdle for their breakthrough is their notoriously low conductivity. To address this, we precisely decorate
CdSe nanoparticles with platinum domains of one to three nanometers in diameter by a facile and robust seeded growth method. We demonstrate the transition from semiconductor to metal dominated conduction in monolayered films. By adjusting the platinum content in such solution-processable hybrid, oligomeric nanoparticles the dark currents through deposited arrays become tunable while maintaining electronic confinement and photoconductivity. Comprehensive electrical measurements allow determining the reigning charge transport mechanisms.
