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NanoPower Research Labs

Nanostructured Radioisotope Batteries

Direct Conversion Radioisotope Batteries

Schematic depicting the multilayered structure of the nipi device. The arrows indicate the direction of electron (designated with “-”) and hole “+” transport and subsequent collection to the external contacts of the device.

Advances in microelectronics and MEMS have enabled portable electronic devices to become smaller with enhanced functional. Unfortunately, power systems (e.g., chemical batteries) have not experienced the same advances and often comprise a majority of the volume and weight of these electronic devices. To alleviate this problem, the conversion of the energy emitted by radioisotopes into usable electric power is being investigated. The high energy density of radioisotopes and their long-half lives makes a 1 cm3 radioisotope battery theoretically capable of generated mW’s of power for many years. A direct drive radioisotope converts the radioisotope energy into electricity using a similar mechanism to that of photodiodes converting light into electricity. In the diode structure, electron hole pairs are generated by the incident radiation (alpha / beta particles), which are forced by the internal field of the diode to opposite electrodes thereby generating a usable current. The concept of such devices is not new; however, devices in the past have not achieved long-lived functionality because of radiation degradation. A novel nanostructured design being investigated by the NPRL is a multi-layered n-type / intrinsic / p-type / intrinsic / n-type / intrinsic / p-type / intrinsic /etc (nipi) diode fabricated from III-V semiconductors using organometallic vapor phase epitaxy. The wider active region of the device increases the radiation absorption cross section, while degradation is mitigated by utilizing thinned junction layers and a drift-field assisted carry extraction.

Indirect Conversion Radioisotope Batteries