Solar cells first generation

Table II shows, as an example, the combinations of low and high levels for three factors selected by a design team for an accelerated test Involving photovoltaic solar cells. In column 2 the three factors are seen to be temperature T (50 C, 95 C), relative humidity RH (60%, 85%), and ultraviolet radiation UV (five suns, 15 suns). The eight combinations of the high and low levels are shown, together with the predicted months to failure for each combination. In this example the documentation to support each prediction is symbolically referenced as shown in the last column. The documentation includes assumptions, calculations, references to the literature, laboratory data, computer simulation results, and other related material. Such a factorial table is first completed by each scientist independently. Subsequently, the team alms to generate a single consensus factorial table has the same form as that shown in Table II.

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First, the drift current is calculated in the case of a constant electrical field, as one would expect for very thin bulk heterojunction solar cells. If the width W of the active layer is similar to the drift length of the carrier, the device will behave as a MIM junction, where the intrinsic semiconductor is fully depleted. The current is then determined by integrating the generation rate G = —dP/dx over the active layer, where P is the photon flux ... 

The key ingredient for new ways to harness sunlight is the solar cell, or photovoltaic (PV) cell, a device that absorbs photons from sunlight (or artificial sunlight) and generates an electrical current [9]. Figure 10.6 shows the evolution over time of photovoltaic cells since 1975 [4]. The first photovoltaic cell was a pn junction based on Si and had an efficiency of 5% to 6% [3] at present, Si pn junctions have overall power efficiencies of about 22% (maybe 10% in commerce) at the moment, Si solar cells are expensive but durable. 

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