Versatility of a New π-Conjugated Ladder-Like Polymer in Enhancing Stability and Efficiency of Perovskite Solar Cells
In this study, a new p-type π-conjugated ladder-like polymer, poly(3,3’-(((2-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-6-methylbenzol[1,2-b:4,5-b’]dithiophen-2-yl)-5-methyl-1,4-phenylene) bis(oxy)bis(hexane-6,1-diyl)bis(1,1,1,3,5,5,5-heptamethyltrisiloxane)) (P-Si), has been designed for SnO2-based perovskite solar cells. Our investigation reveals that this π-conjugated ladder-like polymer system decorated with hydrophobic alkyl chains and siloxane chains is supposed to improve the surface morphology and crystallinity of the perovskite films to reduce defect states and enhance the device stability. In addition, the P-Si with a suitable highest occupied molecular orbital energy level (-5.41 eV) can act as a hole transport medium between the perovskite and the spiro-OMeTAD to enhances excellent hole transportation. As results, which can present as high as 21.5% power conversion efficiency (PCE) with 21.3% steady-state PCE. Typically, the device with P-Si modified can retain 98% of the original PCE after being stored in an ambient environment with 20% relative humidity for 120 days, indicating its excellent long-term stability. Furthermore, after aging for 100 h under illumination at maximum power point in nitrogen atmosphere, the device with P-Si modified retains over 98% of its initial performance.