TECHNOLOGY FOCUS - ELECTRONICS - Preferred Element: The organic thin film is used as organic semiconductor layer of organic thin film transistor. The transistor has source electrode and drain electrode. The organic semiconductor layer is used as electric current path between electrodes. The gate electrode controls electric current amount passing through electric current path.    TECHNOLOGY FOCUS - POLYMERS - Preparation (Disclosed): Polymer having repeating unit (I) is obtained by Suzuki coupling reaction of cyclopentane compound of formula (VIIIa).X1,X2,Y1,Y2=same as defined above;andW1=halogen, alkyl sulfonate, aryl sulfonate, aryalkyl sulfonate, boric acid ester or boric acid group.Preferred Polymer: The polymer is preferably of formula (86-90). Repeating unit (I) is preferably of formula (II, V or VI). The polymer has four or more repeating units (II).X1,X2,Y1,Y2=same as defined above;Z1,Z2=(-S-), (-O-), (-N(R1)-) or group of formula (iv-ix), preferably (-S-);R1-R6=H or substituent, and optionally R5 and R6 combined to form a ring, preferably R1-R6 are halogen, 3-60C monovalent cyclic group (in which cyclic group is monocyclic ring, condensed ring, carboxylic or heterocyclic ring), (un)saturated hydrocarbon, hydroxyl, alkoxy, alkanoyloxy, amino, oxyamino, alkylamino, dialkyl amino, alkanoyl amino, cyano, nitro, sulfo, optionally halogen(s) substituted (alkyl, alkoxy sulfonyl, alkyl sulfonyl), sulfamoyl, alkyl sulfamoyl, carboxyl, carbamoyl, alkyl carbamoyl, alkanoyl or alkoxy carbamoyl group;R,R'=terminal group;R"=H or substituent;andr,t=1-500.The polymer further has repeating unit of formula: -(Ar2)-, where Ar2 is optionally substituted bivalent aromatic hydrocarbon or heterocyclic group, preferably group of formula (IV). The organic thin film is formed by vacuum evaporation method, spin coating method, inkjet printing method, dispenser printing method and flexographic printing method. Preferred Definitions:    X1,X2,Y1,Y2=fluorine atom.    EXAMPLE - Dibromo derivative of cyclopentane of formula (76) (100 mg), 2-tributyl stannyl thiophene (290 mg) and tetrakis(triphenyl phosphine) palladium (0) (30 mg) were mixed. Toluene (1 ml) was added and reacted at 120degreesC. The reaction mixture was cooled and concentrated to form fluorinated thiophene polymer of formula (41) (94 mg) with yield of 91%.