Balanced Charge Mobility and Boosted Exciton Dissociation via SnSe 2 ‐Modified Interface for >20% Efficiency in Layer‐by‐Layer Organic Solar Cells

ABSTRACT Unbalanced charge transport is a critical bottleneck in non‐fullerene organic solar cells. Here, we present a strategy to synergistically overcome this limitation in layer‐by‐layer (LbL) processed D18/L8‐BO devices by incorporating two‐dimensional SnSe 2 nanoflakes at the donor/acceptor heterojunction. The dispersed SnSe 2 acts as discrete charge‐transporting bridges between the D18 and L8‐BO layers, optimizing interfacial energetics, facilitating exciton dissociation, accelerating electron transport, and suppressing recombination. Consequently, the electron mobility is significantly enhanced while the hole/electron mobility ratio approaches unity, signifying balanced carrier transport. Thus, the power conversion efficiency increases markedly from 18.92% to 20.03%, with improved short‐circuit current density and fill factor. This work demonstrates a novel strategy of integrating 2D n‐type semiconductors with the LbL systems and provides an effective pathway toward high‐efficiency organic solar cells with balanced carrier transport and boosted exciton dissociation.