Abstract
Reducing the thin film module production cost is a strong focus in the current thin film solar cell research. One possible way to reduce the cost is minimising material consumption by reducing film thickness. Ultra thin CdTe layer will also help to design p–i–n structure solar cells. The standard CdTe layer thickness is normally in the range of 4–5μm. Experimental trials were carried out in order to reduce the CdTe layer thickness below 1μm using close spaced sublimation technique. Simply reducing the CdTe layer thickness induces pinholes in the CdTe layer which results in poor device performance. The film thickness reduction below 1.5μm was achieved by employing a double layer structure. In the process of making CdTe double layer the first layer was deposited at higher substrate temperature (~520°C) and the second layer was deposited at low substrate temperature (~350°C). The maximum cell efficiency of 12.5% was obtained for ~3μm CdTe layer and comparable device performance was obtained for the 1.5μm CdTe layer (11.2%). Further reducing the film thickness below 1.5μm reduces the device performance. Solar cell efficiencies for ~0.8μm and 0.5μm CdTe layers were 9.5% and 5.2% respectively. The Capacitance–Voltage measurements show that the CdTe layer is fully depleted when the thickness is reduced below 1μm. Further, the possible cause for the decrease in efficiency with decrease in CdTe film thickness is discussed in this article.
Published Version
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