Organic Photovoltaic Fabrication and Test Apparatus

<swf width="600" height="500">http://depts.washington.edu/cmditr/media/opvfab.swf</swf> 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).

See wiki article on Physics_of_Solar_Cells