Solar cells superstrate configuration

A schematic cross-section of a p-i-n a-Si H solar cell [11] is shown in Figure 72a. In this so-called superstrate configuration (the light is incident from above), the material onto which the solar cell structure is deposited, usually glass, also serves as a window to the cell. In a substrate configuration the carrier onto which the solar cell structure is deposited forms the back side of the solar cell. The carrier usually is stainless steel, but flexible materials such as metal-coated polymer foil (e.g. polyimid) ora very thin metal make the whole structure flexible [11]. 

Figure 6.2 Schematic diagram of solar cells with extended junctions and an extremely thin absorber (a) Layer structure for a superstrate n-i-p cell in this configuration a highly structured ra-layer is deposited on a transparent conductive oxide (TCO) contact layer, then a conformal absorber layer is deposited, followed by a transparent p-type transport layer and finally a reflective metal contact (b) Band diagram for the n-i-p heterojunction. The valence-band edges Ey) and conduction band edges Ec) for the absorber and transport layers and the electron and hole quasi-Fermi levels are shown (c) Illustration of reduced transport paths in the absorber layer and extended optical paths due to scattering in the heterostructure (d) Extremely thin absorber cell with a comparably shallow structure and a metal back contact in place of a transparent transport layer.

Optical, Weight and Permeability Reoulrements. If the structural member is the front cover of the module (superstrate configuration), it must be optically clear (> 90% transmission) through the solar spectrum of importance to absorption by the solar cell (0.4-1.1 microns). It must also be relatively hard (> 90 shore A durometer), soil repellent, preferably HV absorbing below 0.36-0.37 microns, and non-permeable to oxygen, water vapor, and atmospheric pollutants. If the rigid member is the back cover, it may be opaque. 

Figure 1.2 Comparison of superstrate and substrate solar cell configurations, (a) Superstrate configuration used for CdSjCdTe solar cells, (b) Substrate configuration commonly used for CIGS solar cells.

Figure 3.8 CIGS solar cell configurations (a) superstrate configuration (b) substrate configuration. Adapted from Romeo et al., 2004 with permission from John Wiley Sons, Ltd...

---