Interface engineering of inverted perovskite solar cells to enhance photovoltaic performance and stability

Abstract

Perovskite solar cells (PSCs) have been developed significantly in recent years, the latest record power conversion efficiency (PCE) of PSCs has surged to 25.7% in 2022 from 3.8% in 2009. However, the poor operating stability has become the main obstacles for commercialization. In this thesis, we focus on improving the efficiency and stability of PSCs by following steps. We start with systematically reviewing recent research progress of PSCs, including the basic principle, main challenges, current solutions, and necessary characterization methods. Then we selected the inverted p-i-n perovskite solar cell as baseline devices, with architecture of ITO/NiOx/CsFAMAPbI3-xBrx/PCBM/BCP /Ag and optimized each layer by tuning their spin speeds, surface treatments (UV ozone / Oxygen plasma), concentrations, and annealing temperature of NiOx, perovskite, PCBM and BCP. The optimized baseline device obtained an average PCE over 17% and a champion PCE over 18%. On that basis, we modified the perovskite/ETL interface with PEAI to form 2D/3D-structure perovskite layers and observed an interesting phenomenon that PCE increased after exposing the devices in ambient for certain period of time. In order to release the potential performance for fresh devices, we exposed fresh perovskite films in various humidity for different time periods and obtained a champion device with 20.24% PCE. We further introduced 2PACz as the NiOx HTL modifier and achieved a best PCE of 22.45%. In the meantime, comprehensive characterizations were conducted to investigate the effect under moisture treatment. Thereafter, we replaced NiOx with 2PACz SAM as hole transport layer and obtained higher PCE and better stability. Then we selected four interface modifiers (PEAI, 4-FPEAI, PEABF4, FABF4) to modify the perovskite/PCBM interface and investigated the modification effects in those PSC devices with a series of characterization methods.