Solution-processable silicon naphthalocyanine tetraimides as near infrared electron acceptors in organic solar cells

Two silicon naphthalocyanine electron acceptors , CH 3 O-SiNcTI and 3BSO-SiNcTI, with four strong electron-withdrawing imide groups , were designed, synthesized, and applied in bulk heterojunction organic solar cells (BHJ OSCs). They exhibited strong near-infrared absorption in 300–1100 nm, maximum extinction coefficients of up to 5.2 × 10 5 M −1 cm −1 , deep lowest unoccupied molecular orbital energy levels of −3.92 eV, and good photothermal stability. The power conversion efficiency of BHJ OSCs based on acceptor of 3BSO-SiNcTI reached 4.22%, which is the highest value among solution-processable phthalocyanine or naphthalocyanine derivatives. The measurements of space-charge-limited current, charge recombination, charge collection capability, atomic force microscopy (AFM), and transmission electron microscopy (TEM) were carried out. It is found that BHJ OSCs based on PTB7-Th:3BSO-SiNcTI, have higher and balanced carrier mobility , less charge recombination, better charge transport, and favorable film morphology, which lead to their higher photovoltaic performance . This study indicates the great potential of SiNcTIs as near-infrared chromophores for high-performance electron acceptors in BHJ OSCs. • Soluble silicon naphthalocyanine tetraimides (SiNcTIs) as electron acceptors were designed and synthesized. • SiNcTIs with intense NIR absorption, excellent stability, suitable energy levels, and well solubility are potential acceptors. • The PCE of the bulk heterojunction organic solar cell based on acceptor 3BOS-SiNcTI reached 4.22%.