| Organic optoelectronic functional materials are the foundation of optoelectronic devices. In this paper, a series of star-shaped materials with different optoelectronic functions are designed and synthesized. Devices based on these functional materials as the interlayer for polymer solar cells, the hole transport material for perovskite solar cells and thermally activated delayed fluorescence emitter for organic light-emitting diodes are fabricated, and their structure-property relationships are discussed.In chapter 1, we give a brief introduction of the background of the interlayer for polymer solar cells, the hole transport material for perovskite solar cells and thermally activated delayed fluorescence material, and then propose the research ideas of this thesis.Chapter 2:four alcohol-soluble interlayers, namely TnO, Tnl, TpO and Tp1 were designed and synthesized by introducing diethylamino or phosphate polar groups into the molecules, in which Tnl and Tpl possess additional extended skeleton and hydrophobic alkyl chains. The work function of ITO significantly decreasd after modified by TnO, Tnl, TpO and Tp1. Utilzing TnO and Tnl as interlayres, the inverted polymer solar cells achieved good device performance, with the power conversion efficiencies of 8.62% and 8.80%, respectively. Compared with TnO and Tnl, TpO and Tpl exhibit relatively rough surface, resulting in PCE of 5.30% and 5.12%. Compared with TnO, Tnl is more hydrophobic, which facilitates the active layer spreading out and obtain a better morphology, thus enhanced the device performance.Chapter 3:four star-shaped conjugated compounds with 1,3,5-triazine as a core and fluorene as the arms, namely Tfl, Tf2, Tf1OH and Tf2OH, were designed and synthesized. Compared with Tfl and Tf1OH, Tf2 and Tf2OH possess more π-extended structure and additional n-hexyl chains in the inner fluorene arms. Owing to the diethylamino or diethanolamino end groups, all the compounds exhibited excellent alcohol solubility and interface modification ability. by reducing the work function of ITO effectively. Enhanced device performances were obtained by incorporating these compounds as the cathode interlayers in inverted polymer solar cells with the power conversion efficiency reached 8.97%,8.33%,8.89% and 8.15%, respectively. Since Tfl exhibit the strongest interface dipole among them, the electron separation and extraction process at the interface Tfl are more efficient.Chapter 4:four star-shaped diethylamino functional materials modified with triphenylamine or triphenyl boron as cores and fluorene as the arms were designed and synthesized, namely TA1, TA2, TB1 and TB2. All these materials exhibited remarkable ability to decrease the work function of ITO electrode. Compared with the electron-donating units cored materials of TA1 and TA2, TB1 and TB2 with a electron-withdrawing central core can lower the work function more effectively, which indicate that the electron withdrawing group and polar group group have an synergistic effect and then generating a larger interfacial dipole.Chapter 5:five star-shaped compounds, namely, TFB-OMeDPA, TFT-OMeDPA, TPT-OMeDPA, HFB-OMeDPA and HPB-OMeDPA were designed and synthesized, with the methoxy diphenylamine hole transport units at periphery, fluorene or benzene as π-bridges and benzene ring or triazine as the central core. Varied with the central core and π bridge, the compounds exhibited significant differences in photophysical, electrochemical and thermodynamic properties. Flexible alkyl chain in the fluorene bridge significantly enhance the solubility of the material. Five compounds exhibited suitable HOMO levels. HFB-OMeDPA and HPB-OMeDPA showed good hole transporting ability, with the hole mobility of 1.45 x 10-5 cm2 V-1 s-1 and 1.15 x 10-5 cm2 V-1 s-1, respectively. Perovskite solar cells based on HPB-OMeDPA and HFB-OMeDPA as the hole transport materials achieved good performances, with the power conversion efficiencies of 13.9% and 12.2%, respectively. Moreover, HFB-OMeDPA-based device exhibited less hysteresis.Chapter 6:a series of tetrahedral configurational compounds, namely C-OMeTPA, Si-OMeTPA, Ge-OMeTPA, AD-OMeTPA and ADP-OMeTPA were designed and synthesized. The central cores vary from carbon, silicon, germanium atoms to adamantane, with methoxy-triphenylamine units as the periphery. The, the hole mobility of Ge-OMeTPA and ADP-OMeTPA are 1.4×10-6 cm2 V-1 s-1 and 3.0×10-5 cm2 V-1 s-1, respectively. ADP-OMeTPA based perovskite solar cell device achieved a 13.8% energy conversion efficiency, which is significantly higher than that of Ge-OMeTPA based device.Chapter 7:carbazole based propeller-like compounds, namely H2CzB and H3CzB, are designed and synthesized. The different connection sites significantly affect the photophysical and electrochemical properties of the compounds. Their HOMO levels are-5.40 and-5.18 eV for H2CzB and H3CzB, respectively. Due to the highly distorted structure, H2CzB and H3CzB owned a large optical band gap of 3.28 and 3.36 eV, respectively. Space charge limiting current method evaluated their hole mobility as 1.98 ×10-5cm2V1 s-1 for H2CzB and 1.89×10-6 cm2V-1 s-1 for H3CzB, respectively, which indicates that H2CzB and Spiro-OMeTAD are potential hole transport material.Chapter 8:Three triarylboron-based thermally activated delayed fluorescence (TADF) emitters are designed and synthesized through integrating electron-donating (D) phenoxazine unit and electron-accepting (A) triarylboron unit. Owing to the higly twisted structures arising from the large steric hindrance of tetramethylphenyl group and the adjacent phenoxazine unit, the HOMOs and LUMOs of these molecules are well separated, resulting in small energy gaps (△EST) and effcient reverse intersystem crossing (RISC) process. The donor-acceptor ratio in these molecules significantly influence the rate constant of RISC (kRISC). By consecutively attaching an additional donor into the triarylboron core, a significant improved kRISC can be obtained. Moreover, the increasing phenoxazine units form a rigid structure, thereby it effectively suppresses the non-radiative decay process and renders a high photoluminescence quantum yield (PLQY). Employing these TADF emitters in solution-processed organic light-emitting diodes achieves a maximum external quantum efficiency of 13.9% and slight efficiency roll-off. |
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