Hydrophobic polymer interlayer for highly efficient and stable perovskite solar cells

• An emerging quinone-donor-receptor conjugated polymer (PAQM-DPP) is reported. • A PAQM-DPP/Spiro-OMeTAD bilayer was applied to improve the hole transport. • PAQM-DPP impedes ions migration, moisture penetration, and electrode diffusion. • The unsealed device with PAQM-DPP maintains 90% after 30-50% humidity for 500 h. So far, as the most studied hole transport layer (HTL) material, Spiro-OMeTAD has been widely used in high-performance perovskite solar cells (PSCs). However, the long-term stability of devices containing Spiro-OMeTAD is largely limited by its sensitivity to moisture and ion diffusion. Herein, we report a highly hydrophobic tetrathiophene polymer (PAQM-DPP) with a quinoid-donor-acceptor structure as a chemically tailored modifier to Spiro-OMeTAD HTL for stable PSCs. A robust bilayer could form by strong binding the PAQM-DPP buffer layer to the Spiro-OMeTAD hole transport layer, thus significantly decreasing ions migration and moisture penetration. Under constant illumination conditions (AM 1.5G illumination at ≈ 50°C temperature, in N 2 atmosphere), the non-encapsulated PSCs with hydrophobic polymer/Spiro-OMeTAD bilayer maintained more than 92% PCE for 500 h and exhibited higher tolerance up to 30-50% relative humidity when compared to the device composed of their Spiro-OMeTAD HTL counterpart.