Electrode Whewell at Faraday's request). The anode is now defined as the electrode at which electrons leave the cell and oxidation occurs (indicated by a minus symbol, "−"), and the cathode as the electrode at which electrons enter the cell and reduction occurs (indicated by a plus symbol, "+"). Each electrode may become either the anode or the cathode depending on the direction of current through the cell. A bipolar electrode is an electrode that functions as the anode of one cell and the cathode of another cell. A primary cell is a special type of electrochemical cell in which the
Organic solar cell holes to the negative electrode. In 1958 the photovoltaic effect or the creation of voltage of a cell based on magnesium phthalocyanine (MgPc)—a macrocyclic compound having an alternating nitrogen atom-carbon atom ring structure—was discovered to have a photovoltage of 200 mV. An Al/MgPc/Ag cell obtained photovoltaic efficiency of 0.01% under illumination at 690 nm. Conjugated polymers were also used in this type of photovoltaic cell. One device used polyacetylene (Fig 1) as the organic layer, with Al and graphite, producing an open circuit voltage of 0.3 V and a charge collection efficiency of 0.3%. An Al/poly(3-nethyl-thiophene)/Pt cell had an external