High performance planar p-i-n perovskite solar cells based on a thin Alq₃ cathode buffer layer

As a thin cathode buffer layer (CBL) tris-(8-hydroxyquinoline), aluminum (Alq₃) is successfully introduced into the planar p-i-n perovskite solar cells (PSC) between the PCBM layer and cathode with a device structure of ITO/PEDOT:PSS/CH₃NH₃PbI₃(Cl)/PCBM/Alq₃/Ag. Due to the as-introduced thin Alq₃ CBL, a high performance planar PSC has been achieved with a fill factor (FF) of 72% and maximum power conversion efficiency (PCE) of 14.22%. The PCE value is approximately 29% higher than that of the reference device without Alq₃ CBL. Concerning the results of AC impedance spectra and transient photocurrent measurements, such a remarkable improvement of PCE is mainly attributed to the Alq₃-caused better charge-extraction at the cathode, which is induced by reducing charge accumulation between PCBM and Ag.