Photoactive compound

A compound of formula (I):

• EAG-EDG-EAG (I)
• wherein each EAG is independently a group of formula (V):
• wherein R10 in each occurrence is H or a substituent;
• each X10 to X13 is independently CR13 or N, wherein R13 in each occurrence is H or a substituent;
• and represents a linking position to EDG;
• and EDG is an electron donating group of formula (IIa):
• wherein:
• each X1 and X2 is independently O, S or Se;
• one of Y1 and Y2 is O and the other is CR5R6 wherein each R5 and R6 is independently H or a substituent;
• Ar independently in each occurrence is a monocyclic or polycyclic aromatic or heteroaromatic group;
• Z1 is a direct bond or, together with R2, forms an aromatic or heteroaromatic group Ar1;
• Z2 is a direct bond or, together with R3, forms an aromatic or heteroaromatic group Ar2;
• R1 and R4 are each independently H, a substituent or a divalent group bound to the EAG;
• R2 and R3, independently in each occurrence is H or a substituent;
• p is 0, 1, 2 or 3 and q is 0, 1, 2 or 3 with the proviso that at least one of p and q is at least 1;
• and
• is a point of attachment to the EAG.