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Semitransparent flexible polymer solar cells were manufactured in a full roll-to-roll process under ambient conditions. After encapsulation a silver based circuit was printed onto the back side of the polymer solar cell module followed by sheeting and application of discrete components and vias. The discrete components were white light LEDs, a blocking diode, a lithium ion battery, vias and button contacts in two adjacent corners. The completed lamp has outside dimensions of 22.5 × 30.5 cm, a weight of 50 g and a very flat outline. The battery and components were the thickest elements and measured < 1 mm. A hole with a ring was punched in one corner to enable mechanical fixation or tying. The lamp has two states. In the charging state it has a completely flat outline and will charge the battery when illuminated from either side while the front side illumination is preferable. When used as a lamp two adjacent corners are joined via button contacts whereby the device can stand on a horizontal surface and the circuit is closed such that the battery discharges through the LEDs that illuminate the surface in front of the lamp. Several different lamps were prepared using the same solar cell and circuitry while varying the amount of white LEDs employed and by variation of the number of batteries and the individual battery capacity. The lamp prototype was developed through two early prototypes and the final and serially produced prototype was subjected to field tests in Zambia. Some of the lamps were recovered and the experiences gained with the prototype are presented allowing for further development that takes systemic factors such as the immediate response and spontaneous handling of the lamp by someone with no prior knowledge of the lamp or its workings.
Krebs et al. (Fri,) studied this question.