Reducing Charge Recombination in 2D/3D Heterostructure Perovskite Through Charge Carrier Spin Polarization with 2D Chiral Perovskite

Organic-inorganic hybrid perovskite (OIHP) solar cells (PSCs) are recognized as a highly promising next-generation photovoltaic technology due to their cost-effectiveness, solution processability, and high power conversion efficiencies (PCEs), which have reached up to 26.1%. However, their commercialization is hindered by its instability, leading to ongoing research efforts to improve durability by creation of a 3D/2D OIHP heterostructure, which enhances stability through improved moisture resistance provided by bulky hydrophobic cations. The 3D/2D OIHP heterostructure also provides significant performance advantages in PSCs. Recent studies have primarily focused on addressing challenges at the OIHP/hole transport layer (HTL) interface by suppressing non-radiative recombination through defect passivation and enhancing charge extraction via optimized band alignment. Despite these advances, challenges still remain in charge transport within the 2D OIHP layer, where strong quantum confinement leads to high exciton binding energy and significant charge recombination. While phase modulation has been used to reduce confinement effects, this approach is limited by the complexity of phase control and the associated trade-offs in stability. Consequently, new mechanisms are required to effectively reduce recombination within the 2D perovskite layers.
One promising pathway is the spin polarization of charge carriers via the Chiral-Induced Spin Selectivity (CISS) effect, which can suppress non-radiative recombination by aligning charge carriers' spin states. This eliminates the need for external magnetic fields, as chirality in organic cations within 2D chiral OIHPs can induce spin polarization naturally. We explore spin-dependent carrier dynamics in 2D chiral OIHPs, revealing that circular dichroism (CD) and circularly polarized photoluminescence (CPPL) demonstrate strong spin-orbit coupling in the excited state. Furthermore, Time-resolved circularly polarized photoluminescence (TR-CPPL) shows anisotropic carrier lifetimes, with spin-polarized carriers exhibiting reduced radiative recombination. Incorporating these spin-polarized 2D chiral OIHP layers into 3D/2D heterostructures significantly enhanced PSC performance, with devices achieving superior PCEs compared to their racemic counterparts. These devices maintained 90% of their initial performance after 2000 hours under ambient conditions, demonstrating excellent device stability. This work highlights the potential of using chiral materials for spin-polarized charge transport in PSCs, presenting a novel approach to reducing recombination and improving both efficiency and stability. These findings pave the way for future advancements in high-performance PSCs by integrating quantum mechanical properties into PV technologies.