高效能鈣鈦礦耦合近紅外光有機染料太陽能電池： 機制性探討之全貌分析

Abstract

將近紅外有機染料整合於鈣鈦礦太陽能電池中，仍面臨分子相容性、元件穩定性及有效電荷傳輸等方面的挑戰。本研究開發了一種含硒取代的鄰苯二吡咯近紅外染料（CB-2Se），以克服上述限制。CB-2Se具備較低的能隙（約1.35 eV），顯著增強了對傳統鈣鈦礦材料吸收範圍以外的近紅外區域光子捕獲能力。 為改善非富勒烯受體（NFAs）常見的自聚集問題，本研究透過移除傳統受體如Y6-16中的噻二唑（Tz）單元來結構優化CB-2Se，有效提升其與PCBM的相容性與分散性，並成功形成均勻且有效的塊材異質接面（bulk-heterojunction, BHJ）層。以PCBM:CB-2Se混摻結構作為電子傳輸層的元件，其光電轉換效率達25.18%，開路電壓為1.164 V，短路電流密度為25.71 mA/cm²，填充因子高達84.15%。 此外，利用飛秒瞬態吸收光譜技術，本研究觀察到在CB-2Se與PCBM界面發生了超快的激子解離過程（小於200飛秒），並首次揭示了電洞由CB-2Se回傳至鈣鈦礦層的新穎載子轉移現象，為界面電荷轉移機制提供了重要見解。

Integrating near-infrared (NIR) organic dyes into perovskite solar cells (PSCs) remains challenging due to molecular compatibility, device stability, and efficient charge transport. This study introduces CB-2Se, a selenium-substituted ortho-benzodipyrrole-based NIR dye, specifically designed to overcome these limitations. CB-2Se exhibits a reduced bandgap (~1.35 eV), significantly enhancing photon harvesting in the NIR region, which is typically inaccessible to conventional perovskite absorbers. To deal with self-aggregation issues with non-fullerene acceptors, CB-2Se was structurally optimized by removing the thiadiazole (Tz) unit present in traditional acceptors such as Y6-16. This modification markedly improved compatibility and dispersion within PCBM, leading to a homogeneous and effective bulk-heterojunction (BHJ) layer. Photovoltaic devices utilizing the optimized PCBM:CB-2Se blend demonstrated notable performance enhancements, achieving a power conversion efficiency (PCE) of 25.18%, with VOC of 1.164 V, JSC of 25.71 mA/cm², and an impressive fill factor of 84.15%. Additionally, femtosecond transient absorption spectroscopy revealed ultrafast exciton dissociation (<200 fs) at the CB-2Se:PCBM interface and identified a novel hole back-transfer process from CB-2Se to the perovskite, while offering valuable insights into interfacial charge transfer processes.