Application of the GaSb solar cell in isotope-heated power systems

It is pointed out that, with the technical advancement of the GaSb solar cell, a radioisotope thermophotovoltaic (RTPV) generator will become very competitive compared with thermoelectric systems. The required cell characteristics and the impact which RTPV operation would have on isotope power system design are discussed. Using a computer model of the GaSb cell and various candidate radioisotopes within a reflective cavity, the efficiency, overall power, and power-to-weight ratios were calculated. Test results for current cells are also presented which support the predictions for power output. It is shown that, with existing ²³⁸Pu heat sources operating at 1100°C, a 573 W system should operate at 14.4% efficiency and exhibit a system-level specific power of approximately 9.2 W/kg. Isotopes with higher power densities such as ²⁴⁴Cm could yield efficiencies of 20% and specific powers exceeding 60 W/kg