Enhancing Stability and Performance in Perovskite Solar Cells Through Rationally Designed Phenanthro[9,10-D]Imidazole Derivatives for Tailored Interfacial Engineering

Abstract

Interfacial engineering techniques play a significant role in the development of perovskite solar cells (PSCs). In inverted PSCs, nickel oxide (NiOx) is commonly used as a hole transport material (HTM). The poor interactions at the NiOx/CH3NH3PbI3 (MAPbI3) interface contributed to the low stability and power conversion efficiency (PCE) in devices. To address this issue, dopant-free ultrathin interfacial layers (IFLs) have been introduced between the NiOx and perovskite. These IFLs enhance the chemical interaction between the NiOx and perovskite interfaces and result in improved device performance. Herein, T-shape phenanthro[9,10-d]imidazole derivatives, SR-1 and SR-2, were designed and synthesized. The SR-molecules were employed as IFL materials in p-i-n devices with a device configuration of ITO/NiOx/IFL/MAPbI3/PCBM/BCP/Ag. Notably, the IFLs serve multiple functions: modifying the energy levels of NiOx, improving the surface roughness and crystallinity of MAPbI3, passivating defects, enhancing charge extraction, and reducing trap density at the NiOx/MAPbI3 interface. As a result, the PCEs of both devices with SR-1 and SR-2 IFLs outperformed that of the pristine device. The best performance of 20.3% efficiency with nearly negligible hysteresis was achieved from the device with SR-1. The devices with SR-molecules achieved remarkable thermal stability under ambient air conditions and continuous heating at 60 °C with 50-60% relative humidity.

Keywords: perovskite solar cell, phenanthro[9, 10-d]imidazole, interfacial layer material, Nickel oxide, passivation, Thermal stability