Dicyanomethylenated Acridone And Quinacridone Derivatives With Optoelectronic Functions

Organic optoelectronic functional materials have important applications in organic light-emitting diodes(OLEDs), organic photovoltaics(OPVs), organic field effect-effect transistors(OFETs), sensors, and so on. Design and synthesis novel Ï€-system and study the structure-performance relationship is fundamental research topics in these areas. Quinacridone(QA) derivative have rigid Ï€ skeleton, outstanding stability, and excellent luminescent proerties. The have been used as green-emitters in OLEDs many years ago. A number of N-alkyl quinacridone derivatives have been reported by our group and their polymorphs, self-assembly, electroluminescent and photovoltaic properties have been systemically investigated. The relationship between molecular/intermolecular structures and materials properties has been deeply understood. Acridone has a similar electronic structure to that of QA. Herein, we developed four classes of ?-conjugated systems based on acridone and quinacridone core.1. In chapter II, a series of dicyanomethylenated acridone derivatives, DCNAC-Cn(n = 1, 4, 6) and DPA-DCNAC-C4 were designed and synthesized. Single-crystal analyses and theoretical calculations indicated that DCNAC skeleton is twisted and flexible, which laed to small energy barrier between planar and twisted conformations of the molecules and lead to enhanced nonradiative process(S1â†'S0 conversion). Thus, the compounds show very low quantum efficiencies in solutions and amorphous solids. On the other hand, the molecules are highly emissive because the torsional vibrations of DCNAC can be confined by multiple intermolecular hydrogen bonds, which show interesting crystallization-induced emission(CIE) behavior. While DCNAC-Cn(n = 1,4,6) have nearly identical photophysical properties in solution, their molecular packing in crystals is regulated by modifying the length of alkyl chains, resulting in the tunable emission colors from green to red. DPA-DCNAC-C4 molecule shows intramolecular charge-transfer(ICT) characteristic and strong near-infrared in the crystalline state(707 nm, ΦF = 0.16). Mechanical, thermal, and organic-vapor stimuli can reversibly alter the aggregation phases between crystalline and amorphous states. Therefore, this study presented a stimuli-responsive emission on/off switching system with various emission colors from 560 to 700 nm.2. In chapter III, a new ?-conjugated electrolyte bis(dicyanomethylene)-quinacridone with two octyl-pyridium(DCNQA-Py Br) and a reference electrolyte N,N’-dioctylpyridinium quinacridone(QA-Py Br) were synthesized and employed as a solution-processed cathode interlayer(CIL) for polymer solar cells(PSCs). The PCDTBT:PC71BM based devices inserted with DCNQAPy Br or QAPy Br interlayer exhibited simultaneously increased open-circuit voltage(Voc), short-circuit current(Jsc), and fill factor(FF). Overall, the PCDTBT:PC71BM device incorporating a 13 nm DCNQA-Py Br interlayer or 4 nm QA-Py Br interlayer exhibited power conversion efficiency(PCE) of 6.96% and 6.70%, respectively. Most importantly, compared to QA-Py Br, DCNQA-Py Br has much improved electron transport ability and conductivity. As a result, the DCNQA-Py Br devices only showed slight decrease of electron transport upon increasing the thickness of the CIL, and thus allowing a high PCE with a wide CIL thickness range from 5 nm to 40 nm. The device incorporating a 40 nm DCNQA-Py Br interlayer exhibits a PCE of 5.80%. Furthermore, introducing DCNQA-Py Br as CIL into the devices based on P3HT:PC61BM, and PTB7:PC71BM also led to significantly enhanced device performance, showing high PCEs of 3.91% and 8.23%, respectively. These results confirm DCNQA-Py Br to be a promising CIL material for solution-processed large-area PSCs with different active layers.3. In chapter VI, a series of benzthiadiazole and oligo(3-hexylthiophene) flanked dicyanomethylenated quinacridone derivatives DCNQA-BT-Tn(n = 1, 2, 3) have been designed and synthesized. They showed intense absorption both in visible and near-infared regions. The HOMO energy level gradually increased from DCNQA-BT-T1 to DCNQA-BT-T3, while the LUMO energy levels of the compounds were all at around-3.7 e V. This low-lying LUMO level insures these compounds suitable for electron acceptors in organic solar cells. Bulk-heterojunction OPVs devices have been made using P3 HT as electron donor and DCNQA-BT-Tn as acceptor. As a result, a PCE of 0.74% has been achieved for the P3HT:DCNQA-BT-T1 device. The device showed broad light response ranging from 300 nm to 750 nm. Compared to the traditional P3HT:PCBM device, P3HT:DCNQA-BT-T1 devices show enhanced reponse in NIR region.4. In chapter V, two 11-ring-fused quinacridone derivatives, TTQA and DCNTTQA, were synthesized by ferric chloride mediated cyclization and Knoevenagel reaction. Their energy levels, photophysical propertis and charge transport properties have been fully investigated. There exist strong Ï€-Ï€ interactions between TTQA molecules due to planar geometry of the large Ï€ skeleton. Therefore, TTQA shows poor solubility in common solvents. Replacement of the carbonyl groups(in TTQA) with dicyanoethylene groups(in DCNTTQA) led to a nonplanar skeleton that significantly improved the solubility of DCNTTQA. Moreover, the strong electon withdrawing effect of dicyanoethylene groups rendered DCNTTQA low-lying HOMO and LUMO levels and red-shifted the absorption to the near-infrared region. DCNTTQA exhibits typical p-type transport character and the solution-processed OFETs based on DCNTTQA showed a hole mobility of 0.217 cm2 V-1 s-1.In summary, we have designed and synthesized a class of DCNAC derivatives with intriguing stimuli-responsive emission on/off switching properties. The mechanism of crystallization-induce emission(CIE) and emission on/off switching have been recoverd. We have also designed and synthesized three series of conjugated systems based on DCNQA skeleton and studied their photophysical and electrochemical properties, and applications in PSCs and OFETs. Our studies have offered theoretical basis for exploring new optoelectronic fuctional materials based on DCN AC and DCNQA cores and their applications in OPVs and OFETs.