Donor-functionalized aza-benzannulated perylenediimide-based ternary blend efficient inverted organic solar cells

Abstract

The donor-substituted azabenzannulated perylenediimide (PDI) derivatives, PTZPBI, CBZPBI, and NNDPBI, were designed and synthesized via a Pictet–Spengler reaction between PDI–NH₂ and an aromatic aldehyde in the presence of excess strong acid, forming a heterocyclic ring, followed by aromatization using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The optical and electrochemical properties of PTZPBI, CBZPBI, and NNDPBI were systematically investigated as a fundamental step toward evaluating their potential for use in organic solar cells. The absorption spectra of the cyclized derivatives exhibited a hypsochromic shift compared to their corresponding imine counterparts (1–3) indicating altered optoelectronic properties. The PDI derivatives were incorporated as acceptor units in D18:Y6-based binary organic solar cells (OSCs) to create ternary OSCs by substituting Y6 at various weight ratios (w/w). The addition of CBZPBI as a secondary acceptor in the ternary organic solar cells enhanced the device's performance, yielding enhanced open-circuit voltage (V_OC), short-circuit current density (J_SC), and fill factor (FF). Additionally, it achieved a more balanced charge carrier mobility compared to the binary D18:Y6 devices.