TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: In the organic solar cell the buffer layer is directly on the cathode, the photoactive layer is directly on the buffer layer, and the anode is directly on the photoactive layer. The cathode has a thickness from a first surface contacting the buffer layer to a second surface opposite the first surface, and the cathode comprises M1 or W1 concentration gradient layer which has a thickness of 1/10-1/2 of the cathode thickness, where a concentration of M1 or W1 in the concentration gradient layer decreases in a direction towards the buffer layer. The M1 or W1 doping ratio of a compound of the M1 or W1 concentration gradient layer is according to the: equation y is equal to (c/d)x x (1); equation y is equal to (c/square root of d)x x (2); and equation y is equal to (c/d2)x x (3), where y is M1 or W1 doping ratio of the compound of the M1 or W1 concentration gradient layer, d is the total thickness of M1 or W1 concentration gradient layer, c is M1 or W1 doping ratio of a compound of a non-concentration gradient layer of the cathode, and x is distance from the first surface of the cathode. The M1 or W1 concentration gradient layer comprises many layers each having a thickness of 1-50 nm in a direction from the first surface of the cathode, where each layer of many layers has M1 or W1 doping ratio of the compound of M1 or W1 concentration gradient layer of 0.02-5 mol%. The cathode has a thickness 100-1000 nm. The M1 or W1 concentration gradient layer has a thickness of 10-500 nm. The buffer layer further comprises amorphous zinc oxide or amorphous zinc oxide and crystalline zinc oxide. The organic solar cell further comprises a transparent substrate disposed on a second side of the cathode. The anode is a metal, a metal alloy, a semi-metal and/or a light-transmissible transparent oxide. The photoactive layer comprises an electron provider and an electron acceptor. The buffer layer has a hole-blocking characteristic.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The transparent substrate is glass, polycarbonate, polymethylmethacrylate, polyethylene terephthalate, polyethylene naphthalate, polyimide and/or polyethersulfone.