A two-in-one additive strategy for poly(3-hexylthiophene)-based perovskite solar cells with improved efficiency and stability

<h2>Summary</h2> Poly(3-hexylthiophene) (P3HT) is a low-cost and hydrophobic hole transport material that holds great promise for developing fully printed perovskite solar cells (PSCs). However, the inefficient p-type doping of P3HT and poor contact at the P3HT/perovskite interface often lead to unsatisfactory performance of the P3HT-based PSCs. Here, we introduce a multifunctional additive, 1-dodecanethiol (DDT), to regulate the stacking of P3HT molecules and improve the p-type doping efficacy of the P3HT film (P3HT-DDT). The DDT additive not only improves the hole transport properties of P3HT but also provides effective defect passivation and inhibits iodine migration at the perovskite/P3HT interface. By using this two-in-one additive strategy, the power conversion efficiency (PCE) of the optimized P3HT-based PSC reaches 23.03% with a high open circuit voltage of ∼1.24 V (1.61 eV band gap). The P3HT-DDT strategy is verified to be universal for mixed-halide PSCs by examining different perovskite band gaps between 1.52 and 1.91 eV.