Dual-molecule Reciprocal Doping Strategy for Cathode Interfacial Materials Enabling Over 20.7% Efficiency in Organic Solar Cells

Abstract

Solution-processabled cathode interfacial materials (CIMs) in organic solar cells (OSCs) inherently suffer from limited conductivity and charge transfer capabilities, which in turn restrict device efficiency. In this study, we report a double-doped CIMs, PDINN-CNT2N, which combines organic PDINN with aminated carbon nanotubes through reciprocal doping strategy. This strategy leverages intramolecular self-doping and intermolecular reciprocal doping between the two components to markedly enhance the electron density and charge transport properties of CIMs. Simultaneously, the intermolecular interactions effectively optimize molecular assembly, thereby reinforcing the electron mobility within the films. OSCs utilizing PDINN-CNT2N CIM demonstrate improved conductivity and electron mobility, while also reducing the charge recombination. Consequently, OSCs based on binary D18:L8-BO achieve an efficiency of 20.05% with superior stability. The widespread applicability of this strategy is further confirmed across additional CNT2N-based CIMs and various active layer systems, significantly enhancing the efficiency to 20.72% (certified as 20.33%) in the ternary system. The study provides essential insights into molecular synergistic doping and presents a universal approach for designing high-performance CIMs that are suitable for scalable solution processing.