TY - JOUR
T1 - Synthesis and Properties of Multi-Triarylamine-Substituted Carbazole-Based Dendrimers with an Oligothiophene Core for Potential Applications in Organic Solar Cells and Light-Emitting Diodes
AU - Lu, Jianping
AU - Xia, Ping Fang
AU - Lo, Pik Kwan
AU - Tao, Ye
AU - Wong, Man Shing
N1 - the Hong Kong Research Grants Council (HKBU 2018/05P) for financial support of this work.
PY - 2006/12/1
Y1 - 2006/12/1
N2 - In this paper, we report on the synthesis and properties of a novel series of multi-triarylamine-substituted carbazole-based dendrimers G 2-OTP(n)-G2 (n = 2-5) with an oligothiophene core. The length of the oligothiophene core varied from 2 to 5 thiophene units. It was found that both the absorption and fluorescence emission peaks red-shifted with increasing oligothiophene core length. As a result, the power conversion efficiencies of the as-fabricated solar cells using the composite of these dendrimers and PCBM as the photoactive layer increased with increasing oligothiophene core length, from 0.04% for G2-DTP-G2 to 0.13% for G2-PTP-G2 under AM 1.5 simulated solar illumination at an irradiation intensity of 100 mW/cm2. After a thermal annealing at 150°C for 15 min under nitrogen, however, the devices based on the G2-DTP-G2:PCBM blend exhibited the most dramatic improvement and almost best performance, although other devices also showed some improvement. Since only G2-DTP-G2 is the a crystalline material among these four dendrimers, the dramatic improvement of the associated devices after annealing is attributed to the formation of some nanocrystalline structures in the active layer, as indicated by DSC analysis and AFM studies. In addition, we have demonstrated that both G2-DTP- G2 and G2-PTP-G2 can be used as hole-transporting emitters in organic light-emitting diodes (OLEDs) with 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) as a hole-blocking layer and LiF/Al as the cathode. Because of the low hole injection barrier, the turn-on voltages of the OLED devices were as low as 4 V. G2-DTP-G2 exhibited blue electroluminescence with a maximum luminance of 1660 cd/m 2 at 15.5 V, while G2-PTP-G2 emitted yellow light with a highest luminance of 1000 cd/m2 at 19 V.
AB - In this paper, we report on the synthesis and properties of a novel series of multi-triarylamine-substituted carbazole-based dendrimers G 2-OTP(n)-G2 (n = 2-5) with an oligothiophene core. The length of the oligothiophene core varied from 2 to 5 thiophene units. It was found that both the absorption and fluorescence emission peaks red-shifted with increasing oligothiophene core length. As a result, the power conversion efficiencies of the as-fabricated solar cells using the composite of these dendrimers and PCBM as the photoactive layer increased with increasing oligothiophene core length, from 0.04% for G2-DTP-G2 to 0.13% for G2-PTP-G2 under AM 1.5 simulated solar illumination at an irradiation intensity of 100 mW/cm2. After a thermal annealing at 150°C for 15 min under nitrogen, however, the devices based on the G2-DTP-G2:PCBM blend exhibited the most dramatic improvement and almost best performance, although other devices also showed some improvement. Since only G2-DTP-G2 is the a crystalline material among these four dendrimers, the dramatic improvement of the associated devices after annealing is attributed to the formation of some nanocrystalline structures in the active layer, as indicated by DSC analysis and AFM studies. In addition, we have demonstrated that both G2-DTP- G2 and G2-PTP-G2 can be used as hole-transporting emitters in organic light-emitting diodes (OLEDs) with 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) as a hole-blocking layer and LiF/Al as the cathode. Because of the low hole injection barrier, the turn-on voltages of the OLED devices were as low as 4 V. G2-DTP-G2 exhibited blue electroluminescence with a maximum luminance of 1660 cd/m 2 at 15.5 V, while G2-PTP-G2 emitted yellow light with a highest luminance of 1000 cd/m2 at 19 V.
UR - http://www.scopus.com/inward/record.url?scp=33846376761&partnerID=8YFLogxK
U2 - 10.1021/cm062111o
DO - 10.1021/cm062111o
M3 - Journal article
AN - SCOPUS:33846376761
SN - 0897-4756
VL - 18
SP - 6194
EP - 6203
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 26
ER -