Heterocyclic compound and heterocyclic polymers

A polymer having a repeating unit of the following formula (IV):

• wherein R3 represents a substituent;
• the combination of A1 and A2 is a combination of —S— and —N═, a combination of —O— and —N═, a combination of —Se— and —N═, or a combination of —S— and —Si(R2)═,
• wherein R2 represents a hydrogen atom or an optionally substituted hydrocarbon group;
• and
• one of two linkages each represented by a solid line and a dashed line is a single bond, while the other is a double bond and
• wherein (A) the polymer has a structure containing consecutively connected 7 or more of the repeating units (Condition A), and
• (B) the proportion of the total number of direct bonds forming a head to tail (HT) bond with respect to the total number of direct bonds between the plurality of repeating units contained in the polymer is 60% or more (Condition B).