**Author details**

of the carriers leads to a strong overall suppression of the yield such that it never reaches one. To have clear understanding, again we refer to the spectral information. **Figure 9** represents the yield and corresponding LDOS. The LDOS is represented in the bulk part (far from the interface) and also at the interface for different injection energies. The electronic structure in the bulk part gives a view of all possible polaronic bands and the energy gap regimes. For a given injec-

*V* = −1*eV* for the given electron-phonon coupling constant *α* and different electron-hole recombination rate Γ*R*. The

The charge carriers lying in a polaronic band can evacuate and arrive at the electrodes. On the other hand, the charge carriers localized in the bound state in the gap recombine quickly and cannot lead to photovoltaic current which diminishes the yield. Through this physical interpretation, yield values around the red marked points are in good agreement with the corresponding electronic structure. As shown, the long-range Coulomb interaction leads to an intricate spectrum with many localized and nearly localized states. This tendency to localizing the spectrum induces a lowering of the efficiency of the cell. **Figure 10** represents the

The aim of this chapter was to acquire a deep understanding of the working mechanism of excitonic solar cells and to improve the device performance. Therefore, we developed a new quantum formalism based on the wave function of excitonic solar cells. The basic idea of this new methodology was shown through the example of two-level excitonic solar cells. We

bands and also localized states in the energy gap (compared to the bulk DOS).

**Figure 10.** Yield as a function of incoming electron energy *ε*<sup>0</sup>

42 Solar Panels and Photovoltaic Materials

legend presented in the first panel is valid for all the other panels.

, the electronic structure may contain the energy states on the allowed polaronic

) on the yield. The effects of recombination can be detected through

in the presence of long-range electron-hole interaction

tion energy *ε*<sup>0</sup>

effect of recombination (Γ*<sup>R</sup>*

**4. Conclusions**

the global reduction of yield.

Tahereh Nemati Aram1,2\* and Didier Mayou<sup>1</sup>

\*Address all correspondence to: th.nemati@gmail.com

