Insights into photovoltaic properties of ternary organic solar cells from phase diagrams

Efficient Nonhalogenated Solvent-Processed Ternary All-Polymer Solar Cells with a Favorable Morphology Enabled by Two Well-Compatible Donors

The rational design of the morphology of ternary all-polymer solar cells (all-PSCs) having broadened photon harvesting is crucial to achieve high device performance. However, multicomponent blends often illustrated an unfavorable morphology such as large-sized phase separation due to their complicated interaction. Herein, we proposed to solve these problems by employing two donors with good miscibility (J51 and PTB7-Th), which also have similar compatibility with the acceptor (N2200). The resultant ternary blend films of J51:PTB7-Th:N2200 feature a uniform phase separation morphology due to the reduced competitive effect of intermolecular interactions. As an additional polymer donor, PTB7-Th could not only enhance the absorption of the binary blend but also act as a crystallization regulator to boost the face-on orientation in ternary blends. Accordingly, the J51:PTB7-Th:N2200 ternary blends exhibited improved sunlight absorption and higher and well-balanced carrier mobility accompanied by enhanced carrier extraction. With the nonhalogenated cyclopentyl methyl ether as the processing solvent, the ternary all-PSCs showed outstanding power conversion efficiency (PCE) higher than 9% when varying the PTB7-Th weight ratio in donors from 20 to 50%. Due to the PTB7-Th content holding a 30% weight ratio in donors, the ternary all-PSCs demonstrated the optimal PCE of 9.60%, which perform better than those of binary all-PSCs (PCE = 7.58 or 5.63%).

Counter Anion Effect on the Photophysical Properties of Emissive Indolizine-Cyanine Dyes in Solution and Solid State

Near-infrared emissive materials with tunable Stokes shifts and solid-state emissions are needed for several active research areas and applications. To aid in addressing this need, a series of indolizine-cyanine compounds varying only the anions based on size, dipole, and hydrophilicity were prepared. The effect of the non-covalently bound anions on the absorption and emission properties of identical π-system indolizine-cyanine compounds were measured in solution and as thin films. Interestingly, the anion choice has a significant influence on the Stokes shift and molar absorptivities of the dyes in solution. In the solid-state, the anion choice was found to have an effect on the formation of aggregate states with higher energy absorptions than the parent monomer compound. The dyes were found to be emissive in the NIR region, with emissions peaking at near 900 nm for specific solvent and anion selections.