本計畫預定為期兩年，目標是要透過系統性的分子設計與合成以開發具有寬電子能隙之有機共軛分子以期能在非線性吸收型可見光限幅器與有機薄膜太陽能電池中將之作為光敏組件。雖然要單一調控共軛結構之電子能隙大小的任務並不困難，但若要結合其他的物理特性並設計出符合應用端需求的分子結構，其挑戰性即被大大地提高。在本計畫中，我們將專注於開發兩類寬能隙共軛分子: 第一類為線性吸收截止點~500nm的分子; 第二類為能隙大小約在1.8eV的分子。此兩類分子在結構上的要求有相當的差異。理論上，具有寬能隙的分子其雙光子吸收帶的短波部分即可能涵蓋至可見光區，而為增強其雙光子吸收度，我們擬開發多取代丁二烯衍生物及富含高極化性pi-電子的新型含雜環之多併環單元並將之引入模型分子中作為共軛結構之一部分，預期可以大幅提升其非線性吸收能力(計畫內文中詳述)以應用於非線性吸收型可見光限幅器。前述的含雜環之多併環結構單元若將其視為推電子基，配合強度適當的拉電子基即可建構出同時具有寬能隙以及高莫爾吸收係數的共軛分子並可應用於有機薄膜太陽能電池中作為短波段吸光材料。此類材料若是推-拉電子單元的強度以及共軛結構大小搭配得當，預期可以增進元件的開路電壓與短路電流進而提高元件的光電轉換效率(計畫內文中詳述)。本計畫所開發出來的材料其光電性質的鑑定包括線性/非線性光學性質量測及製成電池元件後的相關電性量測。其中，線性/非線性光學性質的量測可利用本實驗室的光譜及光學設備獨立完成。我們同時也會進行膜態樣品的所有光學量測以便評估其發展成為固態元件的可行性；至於太陽能電池的應用研究將採合作模式，由本實驗室提供材料而與本實驗室有密切合作的單位進行元件製備與測試。 ;We have proposed a two-year research project and aimed to develop novel wide-bandgap conjugated structures that may be used as the active components in optical power-limiters working in the visible region and the short-wavelength photo-sensitizers in thin-film organic solar cells. We will focus on the molecular design to achieve two groups of conjugated structures: The first one manifests cut-off absorption (lambda cut-off)~ 500 nm and the second one possesses HOMO-LUMO bandgap (Eg) ~1.8 eV. For the model chromophores to be used as effective two-photon optical power-limiters working in the visible, we plan to develop multi-substituted 1,3-butadiene skeletons and various novel polyarenes that possess many polarizable pi-electrons and introduce them into the pi-frameworks of the targeted model chromophores. When appropriately functionalized, we expect the molecular two-photon absorptivity of the resulting chromophores can be promoted especially within the visible (detailed in the proposal). As for the short-wavelength absorbers in organic solar cell, we plan to connect the aforementioned polyarene units with various weak electron-acceptors to accomplish chromophores manifesting their HOMO and LUMO energy levels at appropriate positions so that the open-circuit voltage (VOC) and the short-circuit current density (JSC) of the resulting solar cell can be enhanced and lead to higher power conversion efficiencies (PCEs) (detailed in the proposal). We will independently characterize the related nonlinear optical properties of the designed model compounds by the corresponding optical facilities in our laboratory and as for the photovoltaic properties characterization, at current stage, we will send our samples to our close collaborators for the cell fabrication and related measurements.
