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Optimizing the Phase-Separated Domain Size of the Active Layer via Sequential Crystallization in All-Polymer Solar Cells
摘要： Proper domain size of the active layer plays a key role in determining the exciton dissociation and charge transport in all polymer solar cells (all-PSCs). However, fine-tuning the domain size remains challenging due to low glass transition temperature and negligible mixing entropy in polymer blends. Herein, we systematically studied the influence of “crystallization kinetics” on the domain size and proposed that if donor and acceptor crystallize simultaneously, it is prone to form large domain size; while if sequential crystallization of donor and acceptor occurs, a fine phase separation structure with proper domain size can be obtained. Taking PBDB-T/PNDI blends for instance, the domain size was decreased by using sequential crystallization, meanwhile, the crystallinity and molecular orientation were optimized as well, boosting the power conversion efficiency (PCE) from 6.55% to 7.78%. This work provides a novel way to finely tune the heterojunction phase separation structures.
关键词： domain size,crystallization kinetics,sequential crystallization,all-polymer solar cells,phase separation
更新于2025-09-19 17:13:59
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Optimizing domain size and phase purity in all-polymer solar cells by solution order aggregation and confinement effect of the acceptor
摘要： Domain size, phase purity, and the interpenetrating network within the active layer of all-polymer solar cells (all-PSCs) are crucial for efficient charge generation and carrier transport. However, it is a great challenge to decrease domain size and enhance phase purity simultaneously because of the energetically disfavoring polymer-polymer mixing and chain entanglement. In this work, we manipulated the domain size and phase purity of J51:N2200 blends by promoting their solution ordered aggregation and the confinement of acceptor N2200 to J51 during phase separation. Thus, three solvents, chloroform (CF), mesitylene (Mes), and cyclopentyl methyl ether (CPME) were selected. The solubility of J51 and N2200 in these three solvents decreases solubility differences between J51 and N2200 increases gradually. Among these three solvents, only in CPME solution, N2200 possesses ordered structures, which reduces nucleation barrier to increase nucleation density and boosts template effect of N2200. During phase separation, the ordered aggregation of N2200 dominates solid-liquid phase separation and has the confinement effect of J51. Thus, the blend films cast from CPME have fine-scale phase separation in contrast to the films from CF. In addition, the "memory" effect of ordered aggregations transferred to films can enforce the order of blend films. As a result, the blend film with small domain size (≈21 nm), interpenetrating network structure, and a higher degree of crystallinity was obtained by processed from green solvent CPME. The improved morphology facilitated charge-generating process and carrier transport, resulting in higher short-circuit current (Jsc), fill factor (FF), and the power conversion efficiency (PCE).
关键词： all-polymer solar cells,domain size,phase purity,solution ordered aggregation,confinement effect
更新于2025-09-11 14:15:04