Electronic processes investigation from ultrafast terahertz in photovoltaic DPPDTT-PCBM films

Abstract DPP-based conjugated polymers exhibit a broad optical absorption and high motilities for hole and electron, all of which will be advantageous to high photocurrents and good fill factors in OPV. However, their power conversion efficiency (PCE) still lag behind other polymer donor materials. In order to understand the reason hindering the PCE improvement, it is especially important to reveal the underlying electronic processes in Donor-Acceptor blending active layer. Through optical pump terahertz probe investigation, we found that the combination of fast exciton separation and long carrier lifetime will convenient to optic-electricity conversion efficiency. Although high charge mobility lead to long carrier lifetime, the difficulty of exciton separation in narrow band gap polymer DPPDTT is a key factor affecting device efficiency.