응집물질 전자전도 연구실

Background Overall performance in various types of optoelectronic and transistor devices is not only given by the intrinsic properties, but also significantly influenced by the electronic coupling at the heterojunction. For example, depending on the band alignment and/or electron redistribution, the electron transport behavior across the interface can be characterized by Ohmic or Schottky contact. For the heterojunction electronic structure, a full ab initio description is still computationally unfeasible due to the extended system size, and an efficient calculation based on the density function theory (DFT) is prevailing. By using the DFT method and sophisticated treatments, our group studied electronic structure of hybrid perovskite and its heterojunction with carrier extraction materials. In combination with the non-equilibrium Green’s function method, we designed an efficient electron or spin transport channel material based on the graphene nanoribbons. Our studies provide microscopic details of heterojucntion with helpful guidance towards high-performance devices. Despites of substantial amount of defects to be present for the solution processing, the hybrid perovskite solar cell (PSC) exhibits the power conversion efficiency (~25%) comparable to that of the Si-based solar cell. Besides a proper band gap size and a high absorption coefficient, the main reasons are attributed to the defect-tolerant electronic structure and high carrier mobility (101~103 cm2/Vs). Regarding the high carrier mobility, the main origin has been ascribed to an intriguing coupling behavior between a charge carrier and the lattice vibration, or polaron quasiparticles. Our group studied the role of organic cations on the transport behavior of Frohlich (large) polarons [3]. For various types