Interfacial passivation by polylactic acid in perovskite solar cells

Abstract

Perovskite solar cells (PSCs) have attracted a lot of attention in recent years due to their high efficiency. However, this recorded performance (25.5%) is still lower than the theoretical Shockley-Queisser limit due to the defects at the surface and interface of devices. One potential strategy is to passivate the films by polymers for the PSCs owing to the tunable properties of the polymers. Herein, we introduce polylactic acid (PLA) with CH3 and CO functional groups to passivate the interface between the perovskite and hole-transport layers. The FTIR results display the interaction of PLA and perovskite. The hole-only devices demonstrate decreased hole defect density in the PSCs by PLA passivation. Therefore, the PCE of the PSCs increases from 19.3% to 20.6%, and the Voc enhances from 1.07 V to 1.10 V as the device is treated by PLA passivation. Furthermore, PLA passivation improves the stability of the PSCs. The PSC with PLA passivation maintains ∼90% of the initial PCE value, whereas the control device only keeps ∼72% for 14 days. Besides, the PCE of the PSC with PLA passivation can maintain ∼73% of the original value, but the PCE of the control device decreases to ∼45% of the initial value under 60 ± 5% RH for 450 min.