Charge Carrier Dynamics at Carbon/Perovskite Interface: Implications on Carbon-Based HTM-Free Solar Cell Stability

Carbon-based hole transport material (HTM)-free perovskite solar cells (CPSCs) are an innovative device architecture that mitigates inherent challenges associated with record-breaking perovskite solar cells (PSCs), which rely on metal/HTMs, including instability, manufacturing intricacy, and elevated costs. The photovoltaic efficiency and stability of CPSCs are profoundly influenced by the charge carrier dynamics at the interfaces. Herein, the charge carrier dynamics at the carbon(C)-perovskite interface in CPSCs and its implications on photovoltaic performances and stability, an aspect that has received limited exploration thus far are probed, are investigated using transient surface photovoltage (Tr-SPV) and transient photoluminescence measurements. The study reveals that the C-electrode effectively acts as a selective barrier, impeding electrons while facilitating the extraction of holes at the C-perovskite interface. This selective blocking mechanism holds significant implications for improving the performance and stability of CPSCs over HTM-free PSCs with gold(Au) electrodes. The stability of CPSCs is evaluated by measuring shelf life, maximum power point tracking, Tr-SPV, and X-Ray diffraction measurements. By delving into these pivotal aspects, this work aims to contribute to the advancement and understanding of CPSCs for sustainable and efficient energy conversion. This study provides experimental evidence that carbon(C)-electrodes in C-perovskite solar cells act as counter-electrodes that selectively extract holes at the C-perovskite interface and add to the stability by acting as an encapsulator against moisture and ion migration, an aspect that has received limited exploration are probed using transient surface photovoltage and transient photoluminescence measurements coupled with stability studies.image (c) 2024 WILEY-VCH GmbH