Engineering topics
Ding, Liming
Publications and source records attributed to Ding, Liming.
Thermodynamic Properties and Molecular Packing Explain Performance and Processing Procedures of Three D18:NFA Organic Solar Cells
Abstract Organic solar cells (OSCs) based on D18:Y6 have recently exhibited a record power conversion efficiency of over 18%. The initial work is extended and the device performance of D18‐based OSCs is compared with three non‐fullerene acceptors, Y6, IT‐4F, and IEICO‐4Cl, and their molecular packing characteristics and miscibility are studied. The D18 polymer shows unusually strong chain extension and excellent backbone ordering in all films, which likely contributes to the excellent hole‐transporting properties. Thermodynamic characterization indicates a room‐temperature miscibility for D18:Y6 and D18:IT‐4F near the percolation threshold. This corresponds to an ideal quench depth and explains the use of solvent vapor annealing rather than thermal annealing. In contrast, D18:IEICO‐4Cl is a low‐miscibility system with a deep quench depth during casting and poor morphology control and low performance. A failure of ternary blends with PC 71 BM is likely due to the near‐ideal miscibility of Y6 to begin with and indicates that strategies for developing successful ternary or quaternary solar cells are likely very different for D18 than for other high‐performing donors. This work reveals several unique property–performance relations of D18‐based photovoltaic devices and helps guide design or fabrication of yet higher efficiency OSCs.
Synthesis and Luminescence of Yellow/Orange-Emitting Poly[tris(2,5-dihexyloxy-l,4-phenylenevinylene)-alt-(l,3-phenylenevinylene)]s
Soluble yellow/orange-emitting poly[tris(2,5-dihexyloxy-1,4-phenylenevinylene)-alt- (1,3-phenylenevinylene)] derivatives (6) have been synthesized and characterized. These polymers contain oligo(p-phenylene vinylene) chromophores of equal conjugation length, which are linked to a m-phenylene unit. Optical comparison between 6 and its model compound 8 at room and low temperature reveals the similarity in their absorption and fluorescence band structures. The vibronic band structure of 6 is assigned with the aid of the spectroscopic data for 8 at low temperature. Polymers 6 are electroluminescent with emission lambda (sub max), at approximately 565 nm. By using the device configuration of ITO/PEDOT/6/Ca, the polymer exhibits an external EL efficiency as high as 0.46%.