**10. References**


in an a-Si:H-based solar cells were switched from SnO2 to ZnO, the p-layer deposition conditions also had to be reoptimized to obtain the highest efficiency solar cell or module after such switch. A fundamental answer has to be found for the following question: Why is a high-lifetime mono-crystalline silicon wafer easily processed into a low efficiency solar cell? In addition, the following question requires an answer: "Is there a single set of parameters defining stabilized champion solar cells, or are multiple combinations of materials and solar cell parameters (VOC, JSC, and FF) capable of reaching champion level cell efficiencies? Recent observation in the case of CIGS solar cells suggests that there could be

The proprietary nature sometimes hurts the development of correct models. For example, to correctly identify the stability mechanisms in solar cells or modules, all processing detail may have to be known. Often, companies do not wish to make such knowledge public. In these instances, it appears most effective to bring together researchers in a conference or

It is not clear which technologies will "win" in the long run. Thin films have a cost advantage over crystalline Si, provided the durability is comparable and the performance is high enough. Arguments were presented that the benefit from moving from wafer Si to thin

The author would like to thank the many colleagues without who's knowledge, capabilities, and expertise this chapter would not have been possible. This work was supported by the U.S. Department of Energy under Contract No. DE-AC36-08GO28308 with the National

Anderson, T.J., Crisalle, O.D. Li, S.S. & Holloway, P.H. (2003). Future CIS Manufacturing

Attar, G., Muthaiah, A., Natarajan, H., Karthikeyan, H., Zafar S., Ferekides, C. S. & Morel, D.L.

Catalano, A., D'Aiello, R.V., Dresner, J., Faughnan, B., Firester, A., Kane, J., Schade, H., Smith,

*Conference*, (San Diego, CA, 27-30.9.1982), pp. 1421-1422. ISSN 0160-8371 Chambouleyron, I. & Alvarez, F., (1985). Conversion Efficiency of Multiple-Gap Solar Cells

(1994). Development of Manufacturable CIS Processing. *Proceedings of the First World Conference on Photovoltaic Energy*, (Waikoloa, HI, 5.-9.12.1994), pp. 182-185. ISBN 0-

Z.E., Swartz, G. & Triano, A. (1982). Attainment of 10% Conversion Efficiency in Amorphous Silicon Solar Cells *Conference Record of the 16th IEEE Photovoltaic Specialists* 

under Different Irradiation Conditions. *Conference Record of the 18th IEEE Photovoltaic Specialists Conference*, (Las Vegas, NV, 21-25.10.1985), pp. 533-538. ISSN 0160-8371 Contreras, M.A., Nakada, T., Hongo, M., Pudov, A.O., & Sites, J.R., (2003).

ZnO/ZnS(O,OH)/Cu(In,Ga)Se2 Solar Cell with 18.6% Efficiency. *Proceedings of the. 3rd World Conference on Photovoltaic Energy Conversion*, Osaka Japan, paper 2LN-C-08 Cunningham, D.W., Frederick, Gittings, Grammond, Harrer, S., Intagliata, J., O'Connor,

N.,Rubcich, M., Skinner, D., & Veluchamy, P., (2002). Progress in Apollo®

Technology Development. NREL/SR-520-33997, see the entire report

workshop setting to discuss as much of a problem as is possible.

indeed multiple optima.

film products can be calculated.

Renewable Energy Laboratory.

7803-1459-X

**9. Acknowledgement** 

**10. References** 

Technology. *Conference Record of the 29th IEEE Photovoltaic Specialists Conference,* (New Orleans, 5.19-24.2002), pp. 559-562. ISBN 0-7803-7471-1


**21** 

*South Africa*

**Spectral Effects on CIS Modules** 

*Fort Hare Institute of Technology, University of Fort Hare* 

The effect of spectral distribution on the performance of photovoltaic (PV) modules is often neglected. The introduction of multi-junction devices such as Copper Indium Diselenide (CIS) necessitated a concerted investigation into the spectral response on these devices. In part this attributed to the wider spectral response resulting from a combination of different energy band gaps. This in turn implies that the device should have a relatively lower dependence on outdoor spectral content, which depends on a number of factors such as year

The availability of outdoor spectral data, which in most cases is not available, allows for the evaluation of the outdoor response of the CIS technology as the spectrum shifts during the course of the day, during cloud/clear sky condition and seasons. This study reports on the effect of outdoor spectrum, which is different from the reference AM 1.5, on the CIS

In trying to quantify the 'blueness' or 'redness' of outdoor spectrum, Christian *et. al*. adopted the concept of Average Photon Energy (APE) as an alternative (Christian et al., 2002). He defined APE as a measure of the average hue of incident radiation which is calculated using the spectral irradiance data divided by the integrated photon flux density,

> *b i a b e i a*

*APE*

( )

 

*E d*

*q d*

As an indication of the spectral content, high values of average APE indicate a blue-shifted spectrum, whilst low values correspond to red shifted spectrum. Although this concept at

( )

 

time, location, day time and material composition in the atmosphere.

**2. Different outdoor methodologies currently adopted** 

**2.1 The concept of average photon energy** 

where : qe = electronic charge Ei(λ) = Spectral irradiance i(λ) = Photon flux density

**1. Introduction** 

performance parameters.

as in equation 1.

 **While Deployed Outdoors** 

Michael Simon and Edson L. Meyer

(1)

*26th IEEE Photovoltaic Specialists Conference,* (Anaheim, CA, 29.9-3.10.1997), pp. 691- 694. ISBN 0-7803-3767-0

