# Enhancing Stability and Performance in Perovskite Solar Cells through Rationally Designed Phenanthro[9,10‑d]imidazole Derivatives for Tailored Interfacial Engineering

## TL;DR

This paper introduces new materials to improve the efficiency and stability of perovskite solar cells by enhancing the interface between layers.

## Contribution

The study presents rationally designed phenanthro[9,10-d]imidazole derivatives as interfacial layers for perovskite solar cells.

## Key findings

- Devices with SR-1 and SR-2 interfacial layers achieved higher power conversion efficiencies than the control device.
- The best-performing device with SR-1 reached 20.3% efficiency with minimal hysteresis.
- Devices with SR molecules showed excellent thermal stability under high temperature and humidity.

## Abstract

Interfacial engineering plays a significant role in advancing
the
performance and stability of perovskite solar cells (PSCs). In inverted
PSCs, nickel oxide (NiO
x
) is widely used
as a hole transport material (HTM). However, poor interactions at
the NiO
x
/CH3NH3PbI3 (MAPbI3) interface often lead to reduced device
stability and power conversion efficiency (PCE). To address this issue,
dopant-free ultrathin interfacial layers (IFLs) have been introduced
between NiO
x
and the perovskite layer
to enhance the interfacial interactions and optimize the device performance.
In this work, phenanthro­[9,10-d]­imidazole derivatives,
SR-1 and SR-2, were rationally designed and synthesized as IFL materials
in p–i–n devices with a device configuration of indium
tin oxide (ITO)/NiO
x
/IFL/MAPbI3/PCBM/BCP/Ag. These IFLs not only modify the energy levels of NiO
x
but also improve the surface morphology
and crystallinity of MAPbI3, effectively passivate interfacial
defects, facilitate charge extraction, and reduce trap density at
the NiO
x
/MAPbI3 interface.
As a result, the PCEs of both devices with SR-1 and SR-2 IFLs outperformed
those of the pristine device. The best performance of 20.3% efficiency
with nearly negligible hysteresis was achieved from the device with
SR-1. Furthermore, the devices with SR molecules achieved remarkable
thermal stability under continuous heating at 60 °C and 50–60%
relative humidity, highlighting the potential of SR-based IFLs for
stable and efficient PSCs.