TECHNOLOGY FOCUS - POLYMERS - Preferred Structure: The nitrogen-containing structural unit of polycarbonate resin, is represented by structure chosen from formulae (I,II,1-13).Ar11-Ar24 = optionally substituted arylene;R14, R15, R17, R18 = optionally substituted aryl;R19,R20 = alkylene group or oxygen;Y4 = optionally substituted arylene, Ar25-Y5-Ar25;Ar25 = optionally substituted arylene;Y5 = oxygen, sulfur, optionally substituted arylene;e = 0 or 1;X1, X2 = optionally substituted ethylene or vinylene group;R16 = hydrogen atom, 1-6C optionally substituted alkyl or optionally substituted aryl;Y1-Y3 = single bond, optionally substituted (alkylene, cycloalkylene, alkylene ether), oxygen, sulfur or vinylene group;R10 = hydrogen atom or 1-6C optionally substituted alkyl;R11-R13 = halogen atom or 1-6C optionally substituted alkyl; anda-c = 0-4.    TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Structure: The photovoltaic element has sequential arrangement of transparent electrode, electron-accepting organic layer, electron-donating organic layer and back electrode. Alternately, photovoltaic element has sequential arrangement of transparent electrode, transparent n-type inorganic semiconductor layer, electron-accepting organic layer, secondary electron-donating organic layer, primary electron-donating organic layer and back electrode. EXAMPLE - Zinc oxide layer (as transparent n-type inorganic semiconductor layer) of 1500 Angstrom thickness was provided on the cleaned indium tin oxide (ITO) glass (transparent electrode) using argon gas, by RF magnetron sputtering method. Then, electron-accepting organic layer of 400 Angstrom thickness containing perylene tetracarboxylate methyl imide (PL-ME) was formed on the zinc oxide layer, by vacuum spraying method. Subsequently, dichloromethane solution of polycarbonate resin of formula (31) was applied on the electron-accepting organic layer by spin coat method, to form electron-donating organic layer of 400 Angstrom thickness. Then, gold (back electrode) was vacuum-deposited on electron-donating organic layer. A lead wire was attached to the transparent and back electrodes, to form photovoltaic element. The ITO side of photovoltaic element is irradiated with 75 mW/cm2 white light, and its conversion efficiency was measured by applying 6 mV/s. The result showed that Voc, Jsc, ff and conversion efficiency of photovoltaic element were found to be 0.41 V, 0.36 mA/cm2, 0.31 and 0.061%, respectively. FORMULA (31), PAGE 71