Crystalline Alloys of Organic Donors and Acceptors Based on TIPS-Pentacene

Co-crystals of organic semiconductors
can provide model systems
for the study of fundamental optoelectronic properties and also new
functionality. 6,13-Bis­(triisopropylsilylethynyl)­pentacene (TIPS-Pn)
and its fluorinated analogue 1,2,3,4,8,9,10,11-octafluoro-bis­(triisopropylsilylethynyl)­pentacene
(F8TIPS-Pn) form crystalline substitutional alloys during bulk crystal
growth from solution. Alloys can also be formed by blade casting thin
films from solution. The compounds appear to have sufficient geometric
similarity to be miscible in all proportions without inducing long-range
disorder in the solid state. The offsets of the electronic levels
of TIPS-Pn and F8TIPS-Pn in pure form are similar to those found in
bulk heterojunction solar cells. UV/vis spectroscopy and density functional
theory demonstrate the charge
transfer absorption in the alloy crystals corresponds to an excitation
across molecular pairs.