**3.1. Introduction**

4 4 4 4

*CfT*

is fixed to 1/4, as in [5], which gives a good approximation for ambient

4 4

*M*

*M*

h

h

(26)

(27)

*M a*

*C f T*

h

Compared to Carnot efficiency engine the Müser engine efficiency, even when *C* is maximal,

(1 )(1 ) 1 <sup>1</sup> 4(1 )

In the assumption of *Ta*=289.23*K* the maximum efficiency without concentration, i.e. the solar cell sees the sun through a solid angle *ω<sup>s</sup>* is 12.79% which is better than the predicted value of Würfel [7] but still very low, as shown in figure 8. For concentration equal to 10, 100 and *CMAX*,

**Figure 7.** The maximum solar efficiency using Müser engine for different concentration rates (*C*=1, 10, 100 and *Cmax*)

*C f*

é ù - -- = + ê ú - ë û

*M s*

(1 )(1 ) 1 <sup>1</sup> (1 )

é ù - -- = + ê ú - ë û

h

*S M*

*S M*

h h

the efficiency reaches 33.9, 54.71 and 85.7% respectively.

with Carnot Efficiency limit as a function of ambient temperature.

h h

remains low.

If the ratio *Ta*

<sup>4</sup> / *f Ts* 4

58 Solar Cells - New Approaches and Reviews

temperature, *Ta*=289.23*K*, with *Ts*=6000*K*.

Hence, the corresponding *ηS* becomes:

In a quantum converter the semiconductor energy band-gap, of which the cell is made, is the most important and critical factor controlling efficiency losses. Although what seems to be fundamental in a solar cell is the existence of two distinct levels and two selective contacts allowing the collection of photo-generated carriers [2].

Incident photons with energy higher than the energy gap can be absorbed, creating electronhole pairs, while those with lower energy are not absorbed, either reflected or transmitted. The excess energy of the absorbed energy greater than the energy gap is dissipated in the process of electrons thermalisation, resulting in further loss of the absorbed energy. Besides, only the free energy (the Helmholtz potential) that is not associated with entropy can be extracted from the device, which is determined by the second law of thermodynamics.
