Two-Step Templating Strategy Enabled 20.70% Efficiency Layer-by-Layer Organic Solar Cells

Abstract

The uncontrollable diffusion dynamics of the top layer in layer-by-layer organic solar cells (LBL OSCs) often lead to the undesirable phase separation morphology, limiting photovoltaic performance. Herein, we innovatively presented a two-step templating (TST) strategy to systematically regulate the stacking behavior of bottom layer and deposition dynamics of top layer to optimize the active layer morphology. The first step (plasticizating strategy) employed a designed polymer plasticizer PBTP-BDD to modulate chain stacking behavior of D18, which created a primed template that prolonged the deposition dynamics of L8-BO and promoted its ordered self-assembly, achieving a power conversion efficiency (PCE) of 19.95%. The second step (rinsing strategy), using chloroform solvent to selectively rinse plasticized layer, reconstructed this initial template into a thermodynamically stable and structurally ordered state, guiding L8-BO to adopt a more favorable crystal orientation and further boosting the PCE to 20.70%, significantly superior than the control devices (18.53%) and rinsing-only devices (18.94%), demonstrating the notable advantages of TST strategy. Moreover, the TST strategy exhibited exceptional generality, thus achieving an excellent PCE of 18.08% in 300 nm thick-film OSCs. This work provided important foundation and process guidance for the fabrication of high-performance LBL OSCs through synergistic regulation of deposition dynamics.