| 摘要: | 反式鉛鈣鈦礦太陽能電池(Perovskite solar cells，簡稱PSCs)中的電子傳遞層(Electron Transport Layer，簡稱ETL)功能是將鈣鈦礦層吸光所激發的電子萃取後並傳遞至外線路，因此合成出低LUMO能階的高分子就很重要。本研究合成D-A type共軛高分子P-BNBP-BT-CN，Donor為四環共平面結構的BNBP (double B ← N bridged bipyridine)具有高平面性、低LUMO能階的優點，Acceptor為ITN-CN (benzo[c]thiophene-5,6-dicarbonitrile)結構及帶有兩個強拉電子的氰基，能降低LUMO能階，同時屬於路易斯鹼的氰基可與鈣鈦礦層中屬於路易士酸的Pb2+作用，修飾鈣鈦礦層表面的缺陷。另外使用與ITN-CN結構少一個芳香環的Th-CN ( Thiophene-3,4-dicarbonitrile )結構作為Acceptor單元，合成出高分子P-BNBP-Th-CN。高分子P-BNBP-BT-CN及高分子P-BNBP-Th-CN具有有良好的熱穩定性(熱裂解溫度分別為271 ℃及276 ℃)及良好的疏水性(水接觸角分別為96度及93度) ；由兩個高分子各別與PbI2混合後之FTIR穿透光譜顯示P-BNBP-BT-CN結構中之CN(氰)基往低波數位移6 cm-1、P-BNBP-Th-CN結構中之CN(氰)基往低波數位移4 cm-1，證實CN能與Pb2+作用修飾鈣鈦礦層中的Pb2+缺陷；P-BNBP-BT-CN的HOMO與LUMO能階則為-5.48 eV及-3.81 eV，P-BNBP-Th-CN的HOMO與LUMO能階則為-5.51 eV及-3.7 eV，以兩個高分子分別做為ETL所組裝之反式PSCs (吸光層組成為(FAPbI3)0.9(MAPbBr3)0.1 )的光電轉換效率(PCE)值分別是0.42%及0.42%。;Perovskite solar cells (PSCs) employ an electron transport layer (ETL) to extract and transfer electrons from the perovskite layer by exciting with light to the external circuit. Therefore, it is crucial that conjugated polymers ETL should have a low-lying frontier orbital energy level for ETL. In this study, a D-A type conjugated polymer, P-BNBP-BT-CN, was synthesized. The donor component, BNBP (double B ← N bridged bipyridine), is a four-ring planar structure that offers high planarity and a low-lying LUMO energy level. The acceptor component, ITN-CN (benzo[c]thiophene-5,6-dicarbonitrile), contains two strong electron-withdrawing cyano groups. Which can further reduce the LUMO energy level. Additionally, the cyano groups act as Lewis bases, which can interact with the Pb2+ defect in the perovskite layer to passivate the perovskite suface. Another acceptor unit, Th-CN (thiophene-3,4-dicarbonitrile), which lacks one aromatic ring compared to ITN-CN, was incorporated into the polymer to form P-BNBP-Th-CN. Both P-BNBP-BT-CN and P-BNBP-Th-CN exhibit good thermal stability (decomposition temperatures of 271°C and 276°C, respectively) and hydrophobicity (water contact angles are 96 degrees and 93 degrees, respectively). FTIR transmittance spectra of the two polymers mixed with PbI2 show a red-shift of the CN stretching vibration by 6 cm-1 for P-BNBP-BT-CN and 4 cm-1 for P-BNBP-Th-CN, indicating the interaction of CN groups with coordination unsaturated Pb2+. The HOMO and LUMO energy levels of P-BNBP-BT-CN are -5.48 eV and -3.81 eV, respectively, while those of P-BNBP-Th-CN are -5.51 eV and -3.7 eV, respectively. When used P-BNBP-BT-CN and P-BNBP-Th-CN as ETLs in inverted PSCs with a composition of (FAPbI3)0.9(MAPbBr3)0.1 as perovskite absorber, the power conversion efficiency (PCE) values of the corresponding devices based on P-BNBP-BT-CN and P-BNBP-Th-CN are both around 0.42%. |
