Organic Photovoltaic Fabrication and Test Apparatus

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Overview

It takes many trials to perfect the materials and techniques that make for highly efficient organic solar cells. This apparatus at University of Arizona combines a vacuum fabrication area with a inert gas glove box where prototype cells can be tested under controlled circumstance.

The most common test is to generate a voltage vs current curve by experimentally varying the level of light used to excite the cell and by continually changing the load on the cell using a variable voltage power supply (reverse polarity). First a the cell is kept in the dark and a whole series of voltages are applied while the current is measured. Then this series of measurements is repeated while the cell is illuminated. Typical measurements open-circuit voltage (V_oc), short-circuit current (I_sc), fill factor (FF), maximum power output of the device (P_max), voltage at maximum power (V_max), current at maximum power (I_max). A higher Fill Factor means that the cells is operating closer to its theoretical maximum efficiency.

See wiki article on Physics_of_Solar_Cells

Operation

<swf width="642" height="552">http://depts.washington.edu/cmditr/media/opvfab.swf</swf>

Significance

One example of research using performance chararcterization is being being carried out by the Armstrong group at U of A. In this example variations of preparation of the ITO surface can be precisely compared. [[Image:Characterizing and Modifying the ITO/Organic Interface: Organic Solar Cells |thumb|300px|]]

The performance of organic photovoltaics can be drastically affected by the treatment the ITO receives. These treatments can change the ITO’s work function, remove carbon and/or hydroxides and change the relative ratio of In/Sn on the surface. This variability affects device repeatability and the performance of large-area devices