Reaching optimal efficiencies using nanosized photoelectric devices

We study the thermodynamic efficiency of a nanosized photoelectric device and show that at maximum power output, the efficiency is bounded from above by a result closely related to the Curzon-Ahlborn efficiency. We find that this upper bound can be attained in nanosized devices displaying strong coupling between the generated electron flux and the incoming photon flux from the sun.

Figure 1

(Color online) Schematic view of the nanosized photoelectric device. The gray arrows show the different allowed electron transitions. Transitions between the two energy levels are induced by solar photons (upper curved arrows, red) and by nonradiative processes (lower curved arrows, blue).

Figure 2

(Color online) (a) The efficiency at maximum power in a strongly coupled device $\left({\Gamma }_{nr}=0\right)$ as a function of ${\eta }_c$. (b) The corresponding values of the scaled energies $x_l$, $x_r$, and $x_s$. Results are given for different values of the coupling constants ${\Gamma }_l$, ${\Gamma }_r$, and ${\Gamma }_s$.

Figure 3

(Color online) Same legend as Fig. 2 but for a device where nonradiative effects break down the strong coupling condition.