Rational Design of Conjugated Polymers for d-Limonene Processed All-polymer Solar Cells with Small Energy Loss

Green-Processed Non-Fullerene Organic Solar Cells Based on Y-Series Acceptors

The development of environmentally friendly and sustainable processes for the production of high-performance organic solar cells (OSCs) has become a critical research area. Currently, Y-series electron acceptors are widely used in high-performance OSCs, achieving power conversion efficiencies above 19%. However, these acceptors have large fused conjugated backbones that are well-soluble in halogenated solvents, such as chloroform and chlorobenzene, but have poor solubility in non-halogenated green solvents. To overcome this challenge, recent studies have focused on developing green-processed OSCs that use non-chlorinated and non-aromatic solvents to dissolve bulk-heterojunction photoactive layers based on Y-series electron acceptors, enabling environmentally friendly fabrication. In this comprehensive review, an overview of recent progress in green-processed OSCs based on Y-series acceptors is provided, covering the determination of Hansen solubility parameters, the use of non-chlorinated solvents, and the dispersion of conjugated nanoparticles in water/alcohol. It is hoped that the timely review will inspire researchers to develop new ideas and approaches in this important field, ultimately leading to the practical application of OSCs.

Rod-Coil Block Copolymer: Fullerene Blend Water-Processable Nanoparticles: How Molecular Structure Addresses Morphology and Efficiency in NP-OPVs

The use of water-processable nanoparticles (WPNPs) is an emerging strategy for the processing of organic semiconducting materials into aqueous medium, dramatically reducing the use of chlorinated solvents and enabling the control of the nanomorphology in OPV active layers. We studied amphiphilic rod-coil block copolymers (BCPs) with a different chemical structure and length of the hydrophilic coil blocks. Using the BCPs blended with a fullerene acceptor material, we fabricated NP-OPV devices with a sustainable approach. The goal of this work is to clarify how the morphology of the nanodomains of the two active materials is addressed by the hydrophilic coil molecular structures, and in turn how the design of the materials affects the device performances. Exploiting a peculiar application of TEM, EFTEM microscopy on WPNPs, with the contribution of AFM and spectroscopic techniques, we correlate the coil structure with the device performances, demonstrating the pivotal influence of the chemical design over material properties. BCP5, bearing a coil block of five repeating units of 4-vinilpyridine (4VP), leads to working devices with efficiency comparable to the solution-processed ones for the multiple PCBM-rich cores morphology displayed by the blend WPNPs. Otherwise, BCP2 and BCP15, with 2 and 15 repeating units of 4VP, respectively, show a single large PCBM-rich core; the insertion of styrene units into the coil block of BCP100 is detrimental for the device efficiency, even if it produces an intermixed structure.

Recent advances in non-fullerene organic photovoltaics enabled by green solvent processing

Solution-processed organic photovoltaic (OPV) as a new energy device has attracted much attention due to its huge potential in future commercial manufacturing. However, so far, most of the studies on high-performance OPV have been treated with halogenated solvents. Halogenated solvents not only pollute the environment, but are also harmful to human health, which will negatively affect the large-scale production of OPV in the future. Therefore, it is urgent to develop low-toxic or non-toxic non-halogen solvent-processable OPV. Compared with conventional fullerene OPVs, non-fullerene OPVs exist with stronger absorption, better-matched energy levels and lower energy loss. Processing photoactive layers with non-fullerenes as the acceptor material has broad potential advantages in non-halogenated solvents. This review introduces the research progress of non-fullerene OPV treated by three different kinds of green solvents as the non-halogenated and aromatic solvent, the non-halogenated and non-aromatic solvent, alcohol and water. Furthermore, the effects of different optimization strategies on the photoelectric performance and stability of non-fullerene OPV are analyzed in detail. The current optimization strategy can increase the power conversion efficiency of non-fullerene OPV processed with non-halogen solvents up to 17.33%, which is close to the performance of processing with halogen-containing solvents. Finally, the commercial potential of non-halogen solvent processing OPVs is discussed. The green solvent processing of non-fullerene-based OPVs will become a key development direction for the future of the OPV industry.

Constructing a new polymer acceptor enabled non-halogenated solvent-processed all-polymer solar cell with an efficiency of 13.8%

The new polymer donor PS1 can be easily dissolved in a non-chlorinated solvent, and it exhibited a remarkable PCE when processed with 2-methyltetrahydrofuran.