In-situ fabrication of P3HT passivating layer with hole extraction ability for enhanced performance of perovskite solar cell

Metal halide perovskite solar cells (PSCs) have made a great progress in recent years, however, charge recombination and losses at interfaces between the different layers restrict their performance. In the present work, we devised an efficient method that not only passivates the interfacial traps but also enhances charge extraction of the PSC. The chlorobenzene with the addition of Poly(3-hexylthiophene) (P3HT) is used as antisolvent during the spin coating process of the wet perovskite film. In this way, P3HT molecules permeate along perovskite grain boundaries to fill the pinholes and repair interfacial defects of the perovskite film. In addition, the valence band (VB) of the surface of the perovskite layer is thus tuned to form an energy level better aligned with the hole transport layer (HTL). Such a gradient heterojunction structure (GHJ) layer containing P3HT and perovskite provides a rapid channel for hole migration and improves carrier extraction efficiency. The power conversion efficiency of the champion solar cell is up to 20.0% with an open-circuit voltage of 1.18 V, a short-circuit current density of 22.2 mA/cm(2) and a fill factor of 76.2%. Due to the hydrophobicity of the mixture layer, the long-term stability of the devices has been improved as well.