Polymerized Naphthalimide Derivatives as Remarkable Electron-Transport Layers for Inverted Organic Solar Cells

Two polymerized naphthalimide derivatives, named as N-TBHOB and N-DBH, are prepared by quaternization. They exhibit excellent performance as electron-transport layers (ETLs) in inverted organic solar cells (i-OSCs). The results indicate N-TBHOB with a reticulated structure owns a superior performance on electron extraction, electron transport, thickness tolerance, and less carrier recombination compared with N-DBH with linear structure. The i-OSCs based on N-TBHOB with PTB7-Th:PC71BM as the active layer achieve power conversion efficiencies (PCEs) of 10.72% and 10.03% under the thickness of 11 and 48 nm respectively, which indicates N-TBHOB possesses better thickness tolerance than most of organic ETLs in i-OSCs. N-TBHOB also shows more competent performance than N-DBH and ZnO in nonfullerene i-OSCs for comprehensively improved J(sc), V-oc, and fill factor (FF) values. Its i-OSC with PM6:Y6 blend presents a high PCE of 16.78%. The study provides an efficient strategy to prepare ETLs by combining conjugated and nonconjugated units with a reticulated structure in the backbone for high-performance i-OSCs.

Automated summary

In this study, two polymerized naphthalimide derivatives, N-TBHOB and N-DBH, were synthesized and their excellent performance as electron-transport layers (ETLs) in inverted organic solar cells (i-OSCs) was demonstrated. N-TBHOB, with a reticulated structure, exhibited superior performance in electron extraction, electron transport, thickness tolerance, and carrier recombination compared to N-DBH. The i-OSCs based on N-TBHOB achieved high power conversion efficiencies (PCEs) of 10.72% and 10.03% under different thicknesses, indicating its better thickness tolerance. N-TBHOB also showed competitive performance in nonfullerene i-OSCs. Overall, this study provides an effective strategy for preparing high-performance i-OSCs by combining conjugated and nonconjugated units with a reticulated structure.