Conjugated block copolymer and photoelectric conversion device using same

Provided is a conjugated block copolymer which has excellent solubility in solvents and which is capable of forming an organic thin film in which morphology is controlled by a microphase separation. The conjugated block copolymer comprises a bivalent heterocyclic group in a main chain and at least two types of conjugated polymer blocks containing a side chain which is an alykyl group or an alkoxy group which may be substituted with a fluorine atom or a hydroxyl group, and the difference in solubility parameter between the conjugated polymer blocks the solubility parameter of which has a maximum value and a conjugated polymer block the solubility parameter of which has a minimum value is 0.6-2.0.