Nanostructured, Active Organic-Metal Junctions for Highly Efficient Charge Generation and Extraction in Polymer-Fullerene Solar Cells

摘要

Polymer-fullerene heterojunctions have emerged as the lead technology for all-solution-processable organic photovoltaic (OPV) devices with internal quantum efficiencies reaching ～100% and certified power conversion efficiencies > 8% recently reported. These polymer-fullerene blends form effi cient, distributed molecular "bulk" heterojunctions wherein the polymer acts as an electron donor and the fullerene as an elec tron acceptor. The majority of efforts to improve OPV device performance to date have focused on tuning the optical and electronic properties of the blend components, in particular maximizing the open circuit voltage (Voc) by HOMO-LUMO (highest occupied molecular orbital -lowest unoccupied molec ular orbital) engineering and the short circuit current density (J_(sc)) by enhancing optical absorption. Unfortunately, it is often the case that increases in one parameter are offset by decreases in the other as competing extraction and recombination proc esses interact. For an inclusive enhancement in performance of OPV devices based on polymer-fullerene blends it is therefore imperative to develop generic approaches that minimize fun damental losses associated with energy conversion while maxi mizing the V_(oc) and J_(sc).