Enhanced Moisture and Water Resistance in Inverted Perovskite Solar Cells by Poly(3-hexylthiophene)

Poor stability of the perovskite solar cells (PSCs) under humid conditions is always an obstacle to the practical applications of PSCs. Here, a polymer-based strategy to enhance moisture and water resistance of PSCs is presented. Poly(3-hexylthiophene) (P3HT) is used as an additive to be introduced to the electron transport layer (ETL) of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) to study moisture and water resistance of the ETL film and the stability of the device under the humid conditions. The results show that a small amount of P3HT does not result in decreased power conversion efficiency (PCE), and it can improve the aggregation of PCBM, leading to enhanced moisture and water resistance of ETL. The device based on the P3HT/PCBM ratio of 1:30 exhibits a high PCE of 20.84%, with a short-circuit current (Jsc) of 23.27 mA/cm2, an open-circuit voltage (Voc) of 1.10 V, and a fill factor of 81.47%, which is one of the high performances of the inverted PSCs based on the CH3NH3PbI3 (MAPbI3) material. The PCE of the device modified with P3HT can maintain 85.03% for 720 h [relative humidity (RH) 20%], 77.90% for 48 h (60 RH %), 44.31% for 1 h (90 RH %), and 17.43% for 30 min (in water) of its initial PCE value, while the control device can only maintain about 69.41, 47.10, 9.00, and 0.18% of its initial PCE under the same exposure conditions. This work proposes a strategy by using low-surface-energy conjugated polymers to improve the moisture and water resistance of the inverted PSCs.