Hole Transport Bilayer For Highly Efficient And Stable Inverted Perovskite Solar Cells

We demonstrate that using a hole transport bilayer composed of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) and CuI leads to highly efficient and stable inverted, that is, p-i-n, perovskite solar cells (PSCs). The bilayer-based devices had an average power conversion efficiency (PCE) of 19.4% and a maximum PCE of 20.34%. In comparison, devices with a single PTAA interlayer showed an average PCE of 17.7%. Perovskite films fabricated on PTAA/CuI bilayers showed improved crystallinity and larger grain sizes. Data from ultraviolet photoelectron spectroscopy and Mott-Schottky analysis of impedance suggest an increased built-in potential within the device with enhanced upward band bending at the CuI interface. The bilayered HTL devices have minimum current-voltage hysteresis and stable current output at the maximum power point. These devices were stable for more than 4500 h under ambient light in an inert atmosphere.