An Efficient One‐Arrow‐Two‐Hawks Strategy Achieves High Efficiency and Stable Batch Variance for Benzodifuran‐based Polymer Solar Cells

Abstract

With the development of organic solar cells (OSCs), the high-performance and stable batch variance are becoming a new challenge for designing polymer donors. To obtain high photovoltaic performance, adopting polymers with high molecular weight as donors is an ordinary strategy. However, the high molecular weight need to subtly control the reaction time and state, inevitably caused batch-to-batch variations. Herein, a strategy of steric effect is applied to benzodifuran (BDF)-based polymer by introducing different positions of Cl atom, producing two polymers PBDFCl-1 and PBDFCl-2. The more twisted side chains conformation not only achieve the control of moderate molecular weight for PBDFCl-2, but also easily form molecular stacking through adopting BDF unit and maintain sufficient polymeric crystallinity. Due to the optimized stacking mode and good blend miscibility, PBDFCl-2-based device exhibitsa more elegant power conversion efficiency (PCE) of 17.00% compared to PBDFCl-1-based device. This is the highest efficiency record for BDF-based binary OSCs. Meanwhile, the PCE device variation of the different molecular weights for PBDFCl-2 is little, indicating the reduction of the batch variation. Therefore, smartly using steric effect of Cl atom in strong crystalline BDF unit can form efficient molecular stacking regulations and realize the coordination of high-performance and stable batch variance.

Open-Shell Donors and Closed-Shell Acceptors in Organic Solar Cells

“…Moreover, fine tailoring of the molecular structure will effectively modulate the radical characters of donors/acceptors, which can be demonstrated by the obvious changes in chemical/physical properties in OSCs. It will be of great importance to achieve high-performance near-infrared emitters with excellent photovoltaic device performance and stability. − Our studies provided a novel and important guideline for the design of donors and acceptors in OSCs.…”

Asymmetric Π‐Bridge Engineering Enables High‐Permittivity Benzo[1,2‐B:4,5‐b′]Difuran‐Conjugated Polymer for Efficient Organic Solar Cells

“…The electron density at the HOMO/LUMO energy level of copolymers is similarly delocalized over the whole molecular backbone (Figure 1b,c), which is beneficial for charge transport. [20] The HOMO/LUMO energy level of copolymers is gradually deepened along with the thiophene 𝜋-bridge being replaced by furan 𝜋-bridge (Figure 1c), which we attribute to the stronger electronegativity of oxygen atom in furan unit than that of the sulfur atom in thiophene unit. [21][22][23] Interestingly, despite displaying almost identical continuous positive electrostatic surface potential (ESP) of copolymers (Figure 1d), PBDF-TF-BTz presents a larger dipole moment (6.68 debye) than PBDF-dT-BTz (6.02 debye) and PBDF-dF-BTz (6.20 debye).…”

Cost-Effective Cathode Interlayer Material for Scalable Organic Photovoltaic Cells

“…For OPV cells, cathode interlayer (CIL) materials play a critical role in the electron transport and extraction processes. , However, the quantity of material used in the laboratory-scale OPV cell fabrication, typically in the milligram range, is far from sufficient when transitioning to R2R printing, where the materials are required on a scale of 10–100 g for initial processing condition optimization (Figure a). Furthermore, materials in significantly larger quantities are required for full-scale industrial production, and the variation from batch to batch must be eliminated. , Consequently, the simple synthesis and relatively low cost of materials becomes crucial. Additionally, the rate at which CILs are printed in the R2R process remains a significant concern.…”