以雙螯合配位基為高效去活化材料用以增進有機無機混成鈣鈦礦發光二極體之效能

Abstract

有機無機混成之鈣鈦礦材料已被全世界公認為最具潛力的太陽能材料，而近來此種新穎的鈣鈦礦材料也已成為應用於包含雷射、發光二極體以及光偵測器等等光電元件的優良選擇。本論文之主要目標在於製備以溶液製程製作高效能的鈣鈦礦發光二極體元件。我們發現了一個可以經由表面處理而增加鈣鈦礦發光效率的方式。我們將包含了鄰二氮菲、4,4'-聯吡啶及4,7-二苯基-1,10-鄰二氮雜菲等雙螯合配位基旋轉塗佈於鈣鈦礦薄膜之上，發現鈣鈦礦光致發光的亮度可以有效地提升，同時光致發光的生命期也隨之變長，這意味著鈣鈦礦薄膜的缺陷可以被有效的修補。我們推測鈣鈦礦薄膜中不完全配位的鉛離子或是鉛離子的團聚物有可能形成路易士酸，這些情形都可能會造成缺陷的形成。而雙螯合配位基為路易士鹼，能有效的與前述的路易士酸反應因而修補了這些缺陷。此外也以X光光譜、原子力及電子顯微鏡分析鈣鈦礦薄膜的型態，發現在表面處理後並不會有顯著的影響。而單載子電洞元件的結果也顯示鈣鈦礦薄膜的缺陷密度在配位基處理後降低，再次證明先前的推測的正確性。最後，鈣鈦礦發光二極體的量子效率在以鄰二氮菲處理後明顯增加為約二倍。我們預期我們提出的方法將會是一個具一般性的可以增加鈣鈦礦薄膜發光效率的方式也能提升有機金屬鹵化鈣鈦礦發光二極體效率的方法。

Organic-inorganic hybrid perovskites are recognized as a promising candidate for photovoltaic applications. More recently, this emerging type of perovskite materials also becomes highly attractive as active materials for other optoelectronic devices, including lasers, light-emitting diodes (LEDs) and photodetectors. The aim of this thesis is to develop high-performance LEDs based on solution processes. We have found the efficiency of photoluminescence (PL) of CH3NH3PbBr3 thin films can be enhanced after post-deposition surface treatments with bidentate chelating ligands, including 1,10-phenanthroline, 4,4'-bipyridine and 4,7-diphenyl-1,10-phenanthroline (Bphen). The PL intensities of were improved significantly after we spin-coated 1,10-phenanthroline and 4,4'-bipyridine on the thin film surfaces. Meanwhile, the treatments also resulted prolonged PL lifetimes, suggesting the passivation of the defects in the perovskite thin films. The unsaturated or under-coordination Pb ions, which are also Lewis acids, has been considered as one of the origins of the electronic traps in perovskite thin films. Therefore, the chelating ligands, which behaved as Lewis bases, could effectively react with the Lewis acids and passivate the defects. The morphologies of the perovskite films were also examined using X-ray diffraction, atomic force microscopy, and scanning electron microscopy; the results indicated that the surface treatments did not significantly affect the films. Moreover, the lower defect densities, which were deduced from the current-voltage curves of the hole-only devices, after the treatments supported the functions of the above ligands. Finally, perovskite LEDs were fabricated and the device passivated with 1,10-phenanthroline exhibited a nearly doubled quantum efficiency. We anticipate that this approach proposed in this thesis could lead to a general method for improving the PL efficiencies and the device performance.