Perovskite films passivated by a dendrimer toward high efficiency and high stability devices

Abstract

Passivation engineering has become one of the most effective and convenient strategies to enhance the performance and the stability of perovskite solar cells (PSCs). We design a new material, fatty acid-polyamidoamine-COOH (FPC), with sixteen long alkyl chains and eight carboxylic acid functional groups. The carboxylic acid can passivate the Pb defects at the surface and grain boundaries (GBs). Self-arrangement of the FPC molecules on the surface results in improved surface potential. FPC passivation leads to suppressed charge recombination, enhanced charge carrier transport, and increased light-harvesting. The transient absorption measurements confirm the key role of FPC passivation on the recombination at the interface between perovskite and PC61BM layer in PSCs. The power conversion efficiency (PCE) of PSCs modified by FPC increases to 21.01% with Jsc 23.74 mA/cm2, Voc 1.09 V, and FF 81.16%. Furthermore, the hydrophobic long alkyl chains improve the device stability. Under 60 ± 5% relative humidity (RH), the PSCs with FPC passivation maintain ∼90% of the initial PCE for 3500 min, but the control PSCs only keep ∼50% of the origin PCE. In addition, the devices modified by FPC could maintain ∼82% of the initial PCE value under 25 ± 5% (RH) and 30 ± 5 °C ambient environment for 30 days. This work provides a guideline for designing passivants to improve the efficiency and stability of devices.