Achieving Quasi-Fermi level splitting near its radiative limit in efficient and stable 2D/3D perovskite solar Cells: Detailed balance model

Three-dimensional (3D) perovskite solar cells (PSCs) are renowned for their high-power conversion efficiencies (PCEs), yet they face challenges related to performance and stability. This study introduces a new Dion-Jacobson (DJ) 2D-3D lead-free perovskite solar cell (PSC) design with an optimized hole transport layer, reaching a power conversion efficiency (PCE) of 17.32 %. The enhanced performance is primarily attributed to the incorporation of a suitable hole transport layer (HTL), with a slight additional boost from the quantum confinement effect in the 2D DJ perovskite, which also contributes to improved stability. Together, these factors contribute to increased short-circuit current density (JSC) and open-circuit voltage (VOC). Notably, our optimized device exhibits a QuasiFermi level splitting (QFLS) of 1.15 eV and a photoluminescence quantum yield (PLQY) of 7.08 x 10-2, compared to 0.95 eV and 3.07 x 10-5 for conventional 3D PSCs. Capacitance measurements indicate that PTAA as an HTL achieves the highest capacitance at 19.5 nF/cm2, while NiO provides superior overall efficiency. Mott-Schottky analysis further reveals that the device with NiO HTL exhibits the highest built-in potential and optimal performance at voltages exceeding 1 V. These findings highlight the effectiveness of combining DJ 2D perovskites with appropriate HTL materials to enhance both the performance and stability of lead-free PSCs, paving the way for future advancements in sustainable solar energy technologies.