Multi-junction efficiency limits

As discussed in Sect. 7.3.1, fundamental thermodynamics limits conversion efficiency for both single- and multijunction semiconductor PEC devices have also been established in numerous studies. The thermodynamic tandem limit under ideal conditions, i.e., including thermalization loss, but with no overpotential loss, has been calculated at approximately 40% STH. This is consistent with the optical limits shown in Fig. 7.23. It is also substantially higher than the 30% STH limit established for the single-junction case. Moreover, employing advanced multi-exciton device schemes which eliminate part of the thermalization loss, the theoretical tandem limit is further increased to 46% STH [58]. 

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