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.

有机半导体共晶既可作为研究基本光电性质的模型体系，亦可用于开发新型功能。6,13-双(三异丙基硅基乙炔基)并五苯（6,13-Bis(triisopropylsilylethynyl)pentacene，简称TIPS-Pn）与其氟化类似物1,2,3,4,8,9,10,11-八氟-双(三异丙基硅基乙炔基)并五苯（F8TIPS-Pn）在溶液本体结晶过程中可形成结晶型取代合金；二者亦可通过溶液刮涂法制备薄膜合金。这两种化合物几何相似度较高，可按任意比例互溶，且不会在固态中引入长程无序结构。纯态TIPS-Pn与F8TIPS-Pn的电子能级偏移量与本体异质结太阳能电池中的典型值相近。紫外-可见光谱与密度泛函理论（density functional theory，DFT）分析表明，合金晶体中的电荷转移吸收对应分子对间的激发过程。