High-Performance Thick-Film Organic Solar Cells Based on Layer-by-Layer Mutual Doping Strategy

초록

The thickness sensitivity of organic solar cells (OSCs) has become a key challenge for their industrialization. The layer-by-layer (LbL) method is used to prepare pseudo-planar heterojunctions (P-PHJ), which have advantages in constructing vertical phase separation. In thin-film P-PHJ, interlayer permeation can form sufficient D/A interfaces. However, the D/A interface area cannot increase linearly with the thickness of P-PHJ. This work adopts a ternary LbL mutual doping (LbL-MD) strategy to fabricate D1+A/A+D2 active layers, where D18 is the primary donor (D1), D18-Cl is the secondary donor (D2), and L8-BO is the acceptor (A). The thickness tolerance of OSCs is significantly improved along with the optimization of the interpenetrating network structure and molecular arrangement. The OSCs based on D1+A/A+D2 with 160 nm thickness exhibit excellent photoelectric conversion efficiency (PCE) of 20.11%, which is higher than the optimal PCE of 19.09% for the OSCs based on D1/A with 120 nm thickness. When the active layer thickness is 300 nm, the PCE of OSCs based on D1+A/A+D2 can still reach 18.75%, while the PCE of OSCs based on D1/A is decreased to 17.61%. This study proves that the ternary LbL-MD strategy is a feasible approach for improving the thickness tolerance of the P-PHJ OSCs.

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