Acridine-based novel hole transporting material for high efficiency perovskite solar cells

An acridine-based hole transporting material (ACR-TPA) without the spirobifluorene motif is synthesized via non complicated steps. The ACR-TPA film including Li-TFSI and 4-tert-butylpyridine (tBP) additives exhibits a hole mobility of 3.08 × 10⁻³ cm² V⁻¹ s⁻¹, which is comparable to the mobility of the classical spiro-MeOTAD (2.63 × 10⁻³ cm² V⁻¹ s⁻¹), and its HOMO level of −5.03 eV is slightly lower than that of spiro-MeOTAD (−4.97 eV). ACR-TPA layers with different thicknesses are applied to MAPbI₃ perovskite solar cells, where power conversion efficiency (PCE) increases as the ACR-TPA layer thickness increases due to increased recombination resistance and fast charge separation. The best PCE of 16.42% is achieved from the ca. 250 nm-thick ACR-TPA, which is comparable to the PCE of 16.26% for a device with spiro-MeOTAD in the same device configuration. It is thus anticipated that ACR-TPA can be a promising alternative to spiro-MeOTAD because of its lower cost and comparable photovoltaic performance.