| dc.description.abstract | 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%. | en_US |