Development of Tetrabenzoporphyrin-Based Non-Fullerene Acceptor Molecules That Can Be Processed via a Thermal-Precursor Approach

摘要

Tetrabenzoporphyrin (BP) holds attractive characteristics for optoelectronics applications, such as thelarge, rigid π-conjugated framework and high photoabsorption capability. Although BP has poor solubilityin any solvents, thin films of BP can be prepared by depositing soluble precursor CP as a solution and thenheating it to induce the retro-Diels–Alder reaction in situ (Scheme 1). This "thermal precursor approach"would enable straightforward molecular design and clearerunderstanding of the structure–property relationship becauseit largely reduces the need for solubilizing groups that oftenobscure electronic properties of semiconducting moleculesin the thin-film state.In this work, 2CF_3BP, 4CF_3BP and pCNBP equipped with multiple strongly electron-withdrawinggroups have been designed (Fig. 1a), and evaluated as non-fullerene acceptors in organic solar cells(OSCs). These compounds are deposited via the thermal precursor approach together with a commondonor polymer, either P3HT or PTB7, to form bulk-heterojunction (BHJ)-type active layers. The resultingdevices show clear photovoltaic response, proving that the new BP derivatives serve as acceptor in OSCs(Fig. 1b and Table 1). Although the power conversion efficiencies (PCEs) are rather limited (2.04% at best),this result is an important step in developing anovel class of non-fullerene acceptors for OSCs.Further, this is the first example wherein thethermal precursor approach is successfullyemployed for the preparation of polymer–smallmolecule blend films, thereby extending its scopeof applicability. In this presentation, we willdiscuss in detail the relationship among themolecular structure, electronic properties, andthin-film morphology.