Photovoltaic development for alpha voltaic batteries

An alpha voltaic battery utilizes a radioactive substance, which emits energetic alpha particles, that is coupled to a semiconductor p/n junction diode. Alpha voltaics have not been technologically successful to date primarily because the alpha particles damage the semiconductor material, thus degrading the electrical output of the solar cell in just a matter of hours. The key to future development resides in the ability to limit this degradation. Several approaches to solving this problem have been investigated. One approach uses photovoltaic devices which have good radiation tolerance such as InGaP. Another involves the use of non-conventional cell designs, such as a lateral junction n-type/intrinsic/p-type/intrinsic cell, which minimizes the effect of radiation damage on the overall cell performance. A third approach uses an intermediate absorber which converts the alpha energy into light which can be converted by the photovoltaic junction. The intermediate absorbers used in this approach are inherently radiation-hard semiconducting quantum dots. The synthesis of both the quantum dots and the InGaP devices are presented. A summary of the various approaches and resulting performance of the alpha voltaic devices is given.