Photoactive compounds, photoresist compositions including the same, and pattern formation methods

A photoactive compound, comprising:

• an organic cation;
• and
• an anion represented by one of Formulae (5a) to (5c):
• wherein, in Formulae (5a) to (5c),
• each R3 is independently halogen, cyano, substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C3-30 cycloalkyl, substituted or unsubstituted C3-30 heterocycloalkyl, substituted or unsubstituted C6-30 aryl, substituted or unsubstituted C7-30 arylalkyl, substituted or unsubstituted C7-30 alkylaryl, substituted or unsubstituted C6-30 aryloxy, substituted or unsubstituted C3-30 heteroaryl, substituted or unsubstituted C4-30 alkylheteroaryl, substituted or unsubstituted C4-30 heteroarylalkyl, or substituted or unsubstituted C3-30 heteroaryloxy;
• each R3 independently optionally further comprises one or more divalent linking groups as part of its structure;
• a is an integer from 0 to 4;
• when a is 2 or greater, adjacent two or more of R3 together optionally form a ring;
• in Formulae (5a) and (5b), R4 and R5 are each independently hydrogen, substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C3-30 cycloalkyl, substituted or unsubstituted C3-30 heterocycloalkyl, substituted or unsubstituted C6-30 aryl, substituted or unsubstituted C7-30 arylalkyl, substituted or unsubstituted C7-30 alkylaryl, substituted or unsubstituted C6-30 aryloxy, substituted or unsubstituted C3-30 heteroaryl, substituted or unsubstituted C4-30 alkylheteroaryl, substituted or unsubstituted C4-30 heteroarylalkyl, or substituted or unsubstituted C3-30 heteroaryloxy;
• R4 and R5 each independently optionally further comprises one or more divalent linking groups as part of its structure;
• R4 and R5 together optionally form a ring;
• in Formula (5c), R4 to R7 are each independently hydrogen, substituted or unsubstituted C1-30 alkyl, substituted or unsubstituted C3-30 cycloalkyl, substituted or unsubstituted C3-30 heterocycloalkyl, substituted or unsubstituted C6-30 aryl, substituted or unsubstituted C7-30 arylalkyl, substituted or unsubstituted C7-30 alkylaryl, substituted or unsubstituted C6-30 aryloxy, substituted or unsubstituted C3-30 heteroaryl, substituted or unsubstituted C4-30 alkylheteroaryl, substituted or unsubstituted C4-30 heteroarylalkyl, or substituted or unsubstituted C3-30 heteroaryloxy;
• R4 to R7 each independently optionally further comprises one or more divalent linking groups as part of its structure;
• R4 and R5 together optionally form a ring, and/or R6 and R7 together optionally form a ring.