High-Performance and High-Stability all-Polymer Photomultiplication-Type Organic Photodiode Using an NDI-Based Polymer Acceptor with Precisely Controlled Backbone Planarity

Abstract

It is shown that the performance and the operational stability of an all-polymer photomultiplication-type organic photodiode (PM-OPD) can be significantly enhanced by realizing near-ideal spatial isolation of polymer acceptor via a synthetic approach. A series of new naphthalenediimide-based D-A polymer acceptors, PNDI-Ph, PNDI-Tol, and PNDI-Xy, with different degrees of backbone planarity are synthesized. By introducing benzene, toluene, and p-xylene as the donor units, increasing intramolecular torsional angle is expected. Thus, 2D grazing-incidence X-ray diffraction reveals the highest paracrystalline disorder in the PNDI-Xy thin film. Furthermore, PNDI-Xy has the lowest surface energy resulting in the smallest surface energy difference with matrix donor polymer, poly(3-hexylthiophene-diyl) (P3HT). When combined with P3HT, the less aggregated and low surface energy nature of PNDI-Xy results in near-ideal spatial isolation. Consequently, the all-polymer PM-OPD yielded a high external quantum efficiency of 770 000% with specific detectivity of 3.06 x 10(13) Jones. The physics behind the success of PNDI-Xy in PM-OPD is discussed in conjunction with temperature-dependent current density-voltage analyses and drift-diffusion simulations. Furthermore, the use of polymer acceptor enables the resulting PM-OPD to retain its performance for 24 h, with significantly improved operational stability.