Vacuum‐Deposited Bi-ternary Organic Photovoltaics

摘要： Ternary blend organic photovoltaics (OPVs) have been introduced to improve solar spectral absorption and reduce energy losses beyond that of binary blend OPVs, but the difficulties in simultaneously optimizing the morphology of three molecular components results in devices that have generally exhibited performance inferior to analogous binary OPVs. Here we introduce a small molecule-based bi-ternary OPV comprising two individual, vacuum deposited binary bulk heterojunctions fused at a planar junction without component intermixing. In contrast to previous reports where the open circuit voltage (VOC) of a conventional, blended ternary cell lies between that of the individual binaries, the VOC of the bi-ternary OPV corresponds to one of the constituent binaries, depending on the order in which they are stacked relative to the anode. Additionally, dipole-induced energy-level realignment between the two binary segments necessary to achieve maximum efficiency is observed only when using donor-acceptor-acceptor’ dipolar donors in the photoactive heterojunctions. The optimized bi-ternary OPV shows improved performance compared to its two constituent binary OPVs, achieving a power conversion efficiency of 10.6 – 0.3% under AM 1.5G 1 sun (100 mW/cm2) simulated illumination with VOC = 0.94 – 0.01 V, a short circuit current density of 16.0 – 0.5 mA cm?2 and a fill factor of 0.70 – 0.01.