以胍基雙功能設計提升之天空藍鈣鈦礦發光二極體

Abstract

鈣鈣鈦礦光發光二極體（Perovskite light-emitting diodes, PeLEDs）因具備高光致發光量子效率（PLQY）、可調變的發射波長及狹窄的發光光譜，被視為下一代顯示與照明技術的有力競爭者。然而，相較於綠光與紅光 PeLED 已取得顯著進展，高效率且穩定的藍光元件仍面臨嚴峻挑戰，核心問題包括相純度不足、陷阱態密度過高以及能階排列不匹配。本研究即聚焦於系統性地解決上述瓶頸。 本研究於第二章中提出一種雙功能分子工程策略，使用鹽酸4-胍基苯甲酸（4-guanidinobenzoic acid hydrochloride, GBAC）同時作為埋入式界面層與前驅體添加劑。當GBAC應用於埋入式界面時，可顯著提升基底表面潤濕性與前驅液展布性，進而改善鈣鈦礦薄膜的結晶行為與形貌，同時使空穴傳輸層與發光層之間的能階排列更加平順，降低注入障礙。另一方面，作為添加劑時，GBAC中的胍基可與鈣鈦礦中未配位的鉛離子產生靜電作用，鈍化陷阱態並降低非輻射復合；其羧酸基團則可與PEABr（苯乙胺溴化物）末端的胺基形成氫鍵，抑制小n（n = 1–2）相的生成，並促進中高n相的成長，有效提升能量轉移效率。經GBAC雙重處理後製備之元件展現出更佳的光譜穩定性、降低的啟動電壓及提升至10.6%的外部量子效率（EQE），並維持穩定的天藍色發光（約489 nm）。 於第三章中，我們基於目前的研究成果提出後續發展的潛在方向，未來的研究可包括透過氯離子摻雜進一步調控鈣鈦礦能隙，以實現更深藍且符合 Rec. 2100 顯示標準的高色純度藍光發射；亦可探討對鈣鈦礦上表面進行修飾，以鈍化表面缺陷並提升抗濕氣穩定性。此外，開發具備內在抗氧抗濕能力的材料設計策略，有助於提升藍光PeLED在大氣環境中的操作穩定性，推進其實際應用之可能性。最後，本研究所建立的GBAC分子平台亦為未來白光PeLED的實現提供可能基礎，可藉由多色域鈣鈦礦共沉積或與下轉換螢光材料整合達成多波段發光功能。透過上述策略，有望進一步拓展鈣鈦礦發光元件於次世代光電技術中的應用價值與可靠性。 本研究提出的GBAC雙功能工程策略，提供了解決全溴化準二維鈣鈦礦在相分佈、界面工程與缺陷鈍化上的有效方法，為實現高效率、光譜穩定且具商業應用潛力的藍光PeLED奠定了堅實基礎。

Perovskite light-emitting diodes (PeLEDs) have emerged as promising candidates for next-generation display and lighting technologies due to their high photoluminescence quantum yield (PLQY), tunable emission, and narrow spectral bandwidth. Despite remarkable progress in green and red PeLEDs, achieving efficient and stable blue emission remains a significant challenge, primarily due to the poor phase purity, high trap density, and unfavorable energy level alignment. Addressing them forms the central objective of this study. Herein, in Chapter 2, we present a dual-functional molecular engineering strategy using 4-guanidinobenzoic acid hydrochloride (GBAC), applied both as a buried interfacial layer and as an in-bulk additive. When used at the buried interface, GBAC significantly enhances surface wettability and precursor spreading, enabling improved crystallization and film morphology. This additional layer also facilitates a more favorable energy level alignment between the hole transport layer and the perovskite emissive layer, reducing injection barriers. Simultaneously, in the bulk, the guanidinium moiety of GBAC electrostatically coordinates with undercoordinated Pb²⁺ trap states, suppressing the non-radiative recombination, while the carboxylic acid group forms hydrogen bonds with the ammonium end of phenethylammonium bromide (PEABr), reducing the formation of undesirable low-n (n = 1–2) phases and promote the growth of intermediate- to high-n domains, enhancing energy funneling. Devices fabricated with dual GBAC treatment exhibited enhanced spectral stability, reduced turn-on voltage and improved EQE up to 10.6% at sky-blue emission (~489 nm). In Chapter 3, we propose future research directions based on the current findings. First, bandgap tuning toward deeper-blue emission can be achieved via chloride incorporation to meet Rec. 2100 display standards. Second, surface modification of the top perovskite layer could mitigate moisture-induced degradation by passivating surface traps. Third, intrinsic strategies to enhance ambient stability of blue PeLEDs are essential for real-world deployment. Finally, the developed GBAC platform may serve as a stepping stone toward white-light PeLEDs by enabling multi-color emission either through perovskite domain co-deposition or hybrid phosphor integration. This study provides a comprehensive strategy for addressing phase distribution, interfacial engineering, and defect passivation in all-bromide quasi-2D perovskites, paving the way for efficient, spectrally stable, and commercially viable blue PeLEDs.