PHOTOVOLTAIC TECHNOLOGIES (ET4377): INSTRUCTION 2 ...

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PHOTOVOLTAIC TECHNOLOGIES (ET4377): INSTRUCTION 2 LIGHT MANAGEMENT J SC = 17.8 mA·cm -2 under the solar simulator shown in Figure 1. What is the band gap of this material? Question 2: The Rayleigh film Figure 3 a) Consider the interface between two media with refractive index n=a and n=b (Figure 3b). What are the Fresnel coefficients R and T expressed in a and b for irradiance for light with an incident angle of i =0 (perpendicular)? b) Consider the situation in Fig. 3b. A third medium with refractive index n = x is placed between the other two media. What are the effective Fresnel coefficients R and T expressed in a, b and x for irradiance for light with an incident angle of i =0 (perpendicular)? c) Proof that the minimum reflection and maximum transmission is obtained for x ab . Hint: use the function T(x) derived at question 2b. (Which conditions should be valid to have a maximum for T(x)?) Question 3: The AR coating. Figure 4
PHOTOVOLTAIC TECHNOLOGIES (ET4377): INSTRUCTION 2 LIGHT MANAGEMENT In Figure 4 the light beam traveling in the z-direction is shown. The interface between media 1 and 2 is positioned at z=0. The interface between media 2 and 3 is positioned at z=d. The Fresnel coefficients at the interfaces are t 12 , r 12 , t 23 and r 12 . A light beam described by: Ei (z) E0 cos( t kz) z 0 is traveling in the z-direction and is incident on the interface at z=0. a) Give the expression E R (z a) for the reflected light beam at z=-a. b) Give the expression E T (z b) for the transmitted light beam at z=b. c) For which optical thickness is (z a) minimized? E R Question 4: The critical angle glass glass glass TCO TCO TCO 1 •n-a-Si:H absorber 2 absorber 3 absorber back reflector back reflector back reflector Figure 5 Consider the thin film silicon solar cells as depicted in Figure 5. The interfaces between the various layers are not textured but flat. The transparent conductive oxide layer is Aluminum-doped Zinc-oxide. The back reflector is a magic layer, which reflects all the light transmitted through the silicon absorber layer under a certain angle r back in to the cell. The refractive index for Si layer n Si =4.3, transparent conductive oxide n ZnO =1.86, n glass =1.51 and n Air =1. a) What is the minimum angle for the refraction at the r to have all light reflected and the Si-ZnO interface? b) What is the minimum angle for the refraction at the r to have all light reflected and the ZnO-glass interface? c) What is the minimum angle for the refraction at the r to have all light reflected and the glass-air interface? d) For which r angles does the light not escape the Si, ZnO and glass?
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PHOTOVOLTAIC TECHNOLOGIES (ET4377): INSTRUCTION 2 ...

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