Showing papers by "Chunyan Yang published in 2023"

Hybrid Cycloalkyl‐Alkyl Chain‐Based Symmetric/Asymmetric Acceptors with Optimized Crystal Packing and Interfacial Exciton Properties for Efficient Organic Solar Cells

Abstract: Hybrid cycloalkyl‐alkyl side chains are considered a unique composite side‐chain system for the construction of novel organic semiconductor materials. However, there is a lack of fundamental understanding of the variations in the single‐crystal structures as well as the optoelectronic and energetic properties generated by the introduction of hybrid side chains in electron acceptors. Herein, symmetric/asymmetric acceptors (Y‐C10ch and A‐C10ch) bearing bilateral and unilateral 10‐cyclohexyldecyl are designed, synthesized, and compared with the symmetric acceptor 2,2′‐((2Z,2′Z)‐((12,13‐bis(2‐butyloctyl)‐3,9 bis(ethylhexyl)‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2″,3″′:4′,5′]thieno[2′,3′:4,5] pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐ diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (L8‐BO). The stepwise introduction of 10‐cyclohexyldecyl side chains decreases the optical bandgap, deepens the energy level, and enables the acceptor molecules to pack closely in a regular manner. Crystallographic analysis demonstrates that the 10‐cyclohexyldecyl chain endows the acceptor with a more planar skeleton and enforces more compact 3D network packing, resulting in an active layer with higher domain purity. Moreover, the 10‐cyclohexyldecyl chain affects the donor/acceptor interfacial energetics and accelerates exciton dissociation, enabling a power conversion efficiency (PCE) of >18% in the 2,2′‐((2Z,2′Z)‐((12,13‐bis(2‐ethylhexyl)‐3,9‐diundecyl12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2″,3″′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (Y6) (PM6):A‐C10ch‐based organic solar cells (OSCs). Importantly, the incorporation of Y‐C10ch as the third component of the PM6:L8‐BO blend results in a higher PCE of 19.1%. The superior molecular packing behavior of the 10‐cyclohexyldecyl side chain is highlighted here for the fabrication of high‐performance OSCs.

Real‐Time Probing and Unraveling the Morphology Formation of Blade‐Coated Ternary Nonfullerene Organic Photovoltaics with In Situ X‐Ray Scattering

Abstract: Characterizing the bulk heterojunction (BHJ) morphology of the active layer is essential for optimizing blade‐coated organic solar cells (OSCs). Here, the morphology evolution of a highly efficient ternary polymer:nonfullerene blend PM6:N3:N2200 under different blade coating conditions is probed in real‐time by in situ synchrotron X‐ray scattering and in situ ultraviolet‐visible (UV‐vis) spectroscopy. Besides, the morphology of blade‐coated blend films at different conditions is detailed by ex situ X‐ray scattering and microscopic imaging. The ternary blend film exhibited optimized morphology, such as superior molecular stacking structure and appropriate phase separation structure, and boosted photovoltaic performance of the binary blend, as adding a second polymer component to the host polymer:nonfullerene system can balance nucleation and crystallization of polymers and small molecules, facilitating molecular rearrangement to perfect crystallization. Both binary and ternary blends obtained optimized morphology and photovoltaic properties at medium coating speed, mainly attributed to the movement of the polymer and small molecules at the long crystallization and aggregation stage. These findings help understand morphology formation under film drying and provide guidance for optimizing the morphology in blade‐coated OSCs.

Easily Available High‐Performance Organic Solar Cells by Regulating Phenylalkyl Side Groups of Non‐Fused Ring Electron Acceptors

Abstract: Although non-fused ring electron acceptors (NFREAs) have received increasing attention due to their relatively low synthetic costs, the achievement of high efficiencies strongly depends on tedious pre- or/and post-treatments to refine the active layers, which in turn greatly increase fabrication complexity and expense of organic solar cells (OSCs). Nowadays most of the available as-cast devices based on NFREAs are below 12% efficiencies. Herein, phenylalkyl category side groups (CnPh) are employed to construct new NFREAs named BOR-CnPh (n = 3, 4, and 6), which exhibit inherently decent molecular aggregation and thus exclude additional treatments from device fabrication. The modified alkyl spacers of CnPh side groups not only trigger different aggregation of the acceptors, but also regulate the interaction conformations of donor (D) and acceptor (A), and thus D/A interactions. Encouragingly, the pristine PBDB-T:BOR-C4Ph blend delivers intrinsic fibrous networks with dominating face-on orientation, which yields an optimal efficiency up to 13.12%, and ranks as the highest value among as-cast OSCs based on NFREAs. This research provides a practical strategy to control molecular aggregations, interactions, and pristine heterojunction morphologies for easily available and high-performance organic photovoltaics.

Achieving 17.94% efficiency all-polymer solar cells by independently induced D/A orderly stacking

Abstract: All-polymer solar cells (APSCs) with outstanding mechanical and thermal stability are considered as the most potential application in flexible power supply systems. However, the strong interchain entanglement between conjugated polymers...

Morphology Controlling of All‐Small‐Molecule Organic Solar Cells: From Donor Material Design to Device Engineering

Abstract: Compared to polymer-based organic solar cells, all-small-molecule organic solar cells (ASM-OSCs) have garnered significant attention due to their well-defined chemical structures, lower batch-to-batch variation, straightforward synthesis and purification procedures, and easy to modulate properties. Recent developments in small molecule donors have enabled ASM-OSCs to achieve power conversion efficiencies (PCEs) in excess of 17%, gradually approaching those of polymer-based devices, and demonstrating considerable potential for commercialization. However, structural and morphological features in the all-small-molecule blend films, including crystallization behavior, phase separation, and molecular arrangement, play a crucial role in the photoelectric performance. This review systematically introduces and discusses recent advancements in ASM-OSCs in terms of design strategies for novel small molecule donors and device engineering. Additionally, the correlation between active layer morphology and structure and device performance is analyzed. Finally, the challenges and prospects of ASM-OSCs are discussed. This article is protected by copyright. All rights reserved.

A Designed Template Removal Method for Obtaining Mesoporous Films with Highly Ordered Structure by Rapid Thermal Processing Technique

Abstract: The soft-templating methodology is a highly effective approach to prepare ordered organic mesoporous structures. However, in the traditional thermal-induced template removal process, the resultant mesoporous films often suffer from severe shrinkage, which causes a reduction in pore size and order. To overcome these limitations, we developed a strategy that combines rapid thermal processing (RTP) with dynamic circulation. This approach aims to optimize the ordered mesostructures of the films after template removal. The mesoporous structure was evaluated by various analytical techniques, including XRD, NMR, TEM, and grazing incident small angle X-ray scattering (GISAXS). Our results demonstrate that the dynamic thermal processing method leads to a high-quality mesoporous films with significantly reduced shrinkage in the mesoporous structure. Specifically, the d-spacing of mesopores decreased only from 10.4 to 9.1 nm when treated with RTP, which is smaller than the mesoporous films treated using traditional heat processing (reduced to 7.7 nm). Furthermore, dynamic cycling led to an increase in the domain size of the ordered structure from 49.1 to 199.7 nm. These findings were confirmed by cross-sectional TEM, consistent with the values obtained from the GISAXS analysis. Finally, we discuss the feasibility and efficiency of the proposed thermal treatment method, which can provide a straightforward approach to improve the ordered degree in mesoporous films.

Formation of Efficient Quasi-All-Polymer Solar Cells by Synergistic Effect of the Ternary Strategy and Solid Additives.

Abstract: All-polymer solar cells (all-PSCs) have been widely studied owing to their unique mechanical flexibility and stability. However, all-PSCs have a lower efficiency than small-molecule acceptor-based PSCs. In the work, a ternary quasi-all-polymer solar cell (Q-all-PSC) using a synergy of the ternary strategy and solid additive engineering is reported. The introduction of PC71BM can not only match the energy level of the photoactive materials with an improved open circuit voltage (VOC) of the ternary devices but also enhance photon capture, which can improve short circuit current density. It is found that there is effective charge transfer between PC71BM and PY-IT, which can form an electron transport channel and promote efficient charge transport. Moreover, the introduction of PC71BM made the PM6/PY-IT/PC71BM ternary blends more crystalline while slightly reducing phase separation, resulting in a suitable domain size. Importantly, by introducing a high dielectric-constant PFBEK solid additive as the fasten matrix, the Q-all-PSC's efficiency can reach 16.42%. This method provides a new idea for future research on all-polymer solar cells.