HALS-770 interlayer simultaneously block internal and external degradation paths of perovskite for stability and high efficiency perovskite solar cells

The stability of perovskite solar cells (PSCs) is a major problem limiting their application. Here, we proposed a feasible solution using bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (HALS-770) as top protection layer of perovskite. HALS-770 interlayer can not only improve the antioxidant ability of perovskite by removing superoxide (O2·-) with help of hindered amine groups, but also suppress the internal and external degradation path of perovskite due to the co-existence of hydrophilic and hydrophobic groups. Moreover, it can block volatilization of organic cation and the migration of Ag+ and I-, thus improve thermal stability of perovskite and alleviate destruction of Ag electrode. In addition, the heterocycles N atom and carbonyl group in HALS-770 interact with the under-coordinated Pb2+, reducing the interface defects. As a result, the unencapsulated device maintains excellent stability over 95 % of its initial efficiency after 30 days in ambient condition with about 25–50 % humidity, and possesses remarkable continuous operation stability with projected T80 > 1400 h at maximum power point tracking in glove box, much higher than those of the pristine device. Meanwhile, HALS-770 enable the PCE of 21.88 % for PSC (0.06 cm2), which is among the highest efficiencies for MAPbI3 based PSCs with p-i-n structure, and the PCE of 19.07 % for PSM (4 cm2). And it is also suitable for FAMA-based devices with n-i-p structure, enabling an efficiency of 23.03 % (0.06 cm2) and excellent stability.