1 + 1 > 2: Dual strategies of quinolinic acid passivation and DMF solvent annealing for high-performance inverted perovskite solar cell

We developed a new combined method in which quinolinic acid (QA) passivation and DMF solvent annealing are carried out sequentially to enhance the performance of inverted perovskite solar cells. Upon systematic investigation, we found that: 1). One QA molecule not only passivates more than one defects within lattice or neighboring lattices, creating a multi-passivation effect, but also enhances the interactions between lattices, due to pyridine ring and dicarboxylic acid functional groups in the molecule; 2). By combining with DMF solvent annealing post-treatment sequentially, high quality perovskite films with very large grain size over 1 µm are obtained on the substrate of PEDOT: PSS. As a result, the PSC fabricated with the combined method demonstrates an excellent humidity stability and yields a PCE of 18.56% with 20% and 11.6% increment of Voc and Jsc, respectively. To the best of our knowledge, it is the highest reported PCE for inverted PSCs with undoped PEDOT:PSS as hole transporting layer. Therefore, our work indicates that the combined strategy of multi-passivation with QA and solvent annealing with DMF sequentially has a significant potential for highly-efficient and stable inverted planar PSCs.