High‐Efficiency Sequential‐Cast Organic Solar Cells Enabled by Dual Solvent‐Controlled Polymer Aggregation

Abstract

The precise tuning of the active layer morphology to improve organic solar cells (OSCs) efficiency remains a key issue in the field of organic photovoltaics. Herein, a new solution to the above problem is provided by using the dual‐solvent modulated polymer‐assisted sequential spin‐coating method. Herein, the sequential spin‐coated OSCs based on the D18‐Cl/Y6 system are prepared for the first time and an efficiency of 16.38% is obtained, similar to that of bulk heterojunction OSCs. On this basis, the performance is further improved by using a dual solvent to balance the dissolution and crystallization of D18‐Cl, separately optimizing the morphology of the donor layer and allowing the subsequent spin‐coated Y6 solution to penetrate uniformly into the D18‐Cl framework. After the dual‐solvent treatment, the D18‐Cl (CF + CB)/Y6‐based device obtains a power conversion efficiency (PCE) of 17.33% and the D18‐Cl (THF + CB)/Y6‐based device achieves an even better PCE of 17.73%. It is worth noting that no post‐treatment is adopted here and after 2500 h of placement, the efficiency of the aforementioned devices is still 90% of the original. Thus, this work provides a simple method for tuning the film morphology to prepare efficient and stable devices, which is beneficial for future commercial production of OSCs.

Recent Developments of Polymer Solar Cells with Photovoltaic Performance over 17%

“…Li et al. [ 372 ] addressed a dual solvent treatment strategy, which aims to add a second solvent (CF or THF) to the D18‐Cl solution with CB as solvent to balance the dissolution and crystallization of the donor, and optimize the morphology of the D18‐Cl layer. Then the subsequent Y6 solution will penetrate into the D18‐Cl layer uniformly, achieving a suitable vertical phase separation.…”

“…By delicately tailoring the balance of solubility and evaporation rate of acceptor solvent, CF and XY were selected to fabricate gradient phase separation, which benefits the charge transport and endows high PCE even with thick active layers prepared by blade-coating techniques. Li et al [372] addressed a dual solvent treatment strategy, which aims to add a second solvent (CF or THF) to the D18-Cl solution with CB as solvent to balance the dissolution and crystallization of the donor, and optimize the morphology of the D18-Cl layer. Then the subsequent Y6 solution will penetrate into the D18-Cl layer uniformly, achieving a suitable vertical phase separation.…”

Mastering morphology of non-fullerene acceptors towards long-term stable organic solar cells

“…Therefore, it gradually evolves to the equilibrium state, causing the suboptimal morphology 19 , 20 . Some valid strategies like using solid additives 21 , 22 , designing oligomer molecular and polymer acceptors 23 , 24 , establishing structure device 25 , as well as introducing a third donor or acceptor component have been extensively explored to significantly suppress the burn-in losses for NFA-based OSCs 26 . However, almost no state-of-the-art OSCs could deliver a satisfied T 80 lifetime under thermal or illumination stress so far.…”

Efficient and Stable Ternary Organic Solar Cells Using Liquid Crystal Small Molecules with Multiple Synergies

“…With the expanding demand for clean energy, organic solar cells (OSCs), as a promising photovoltaic technology for renewable energy, have become one of the research hotspots in recent years thanks to their benefits, such as light weight, solution processability, large area preparation of flexible devices, and roll-to-roll production. − For the problems of efficiency and stability of OSCs, improvements of active layer materials, device structure process, and regulation of interface layer have been proposed for improvement. − At present, the efficiency of OSCs has reached 20% and is gradually developing toward commercialization requirements. , However, because organic semiconductor materials usually present low exciton diffusion length, thus the widely studied organic solar cell structures are transformed from planar heterojunction (PHJ) to bulk heterojunction (BHJ) . In the BHJ structure, the donor and acceptor are mixed to form a bicontinuous interpenetrating network with a large interfacial area for efficient exciton dissociation .…”