Hidden Structure Ordering Along Backbone of Fused‐Ring Electron Acceptors Enhanced by Ternary Bulk Heterojunction

Abstract

Fused-ring electron acceptors (FREAs), as a family of non-fullerene (NF) acceptors, have achieved tremendous success in pushing the power conversion efficiency of organic solar cells. Here, the detailed molecular packing motifs of two extensively studied FREAs-ITIC and ITIC-Th are reported. It is revealed for the first time the long-range structure ordering along the backbone direction originated from favored end group π-π stacking. The backbone ordering could be significantly enhanced in the ternary film by the mutual mixing of ITIC and ITIC-Th, which gives rise to an improved in-plane electron mobility and better ternary device performance. The backbone ordering might be a common morphological feature of FREAs, providing explanations to previously observed small open circuit voltage loss and superior performance of FREA-based devices and guiding the future molecular design of high-performance NF acceptors.

Multiple Temporal‐Scale Photocarrier Dynamics Induced by Synergistic Effects of Fluorination and Chlorination in Highly Efficient Nonfullerene Organic Solar Cells

“…For the PBDB‐T:ITIC film, we do not observe the distinct ITIC scattering peaks in Figure e, and the 2D GIWAXS pattern of the blend film is almost the same as that of the neat PBDB‐T film, suggesting that PBDB‐T is able to maintain strong crystallinity whereas the crystallinity of ITIC displays a significant decrease. The results further confirm the well compatibility and miscibility between PBDB‐T and ITIC obtained from contact angle data (Figure S13, Supporting Information), agreeing well with the previous reports . For the PBDB‐T‐2Cl:ITIC film, it can be clearly seen that the corresponding (010) π–π stacking peak is mainly from PBDB‐T‐2Cl, which is confirmed by the larger integral area in Figure S15b, Supporting Information.…”

“…For the pure PBDB‐T and PBDB‐T‐2Cl films, the (010) π–π stacking peaks of these two polymer donors are separately located at 17.53 and 17.28 nm −1 in the out‐of‐plane direction and stronger than those in the in‐plane direction, implying the predominant face‐on oriented π–π stacking features . Similarly, neat ITIC and IT4F films also exhibit the more obvious π–π stacking peaks at 15.35 and 17.79 nm −1 in the out‐of‐plane direction, respectively, but very weak (010) peaks in the in‐plane direction, suggesting that these two non‐fullerene acceptors have the preferred face‐on orientation . Moreover, the π–π stacking distance ( d ‐spacing) and crystalline coherence length (CL) can be quantitatively calculated by the equations of d ‐spacing = 2π/ q and CCL = 2π/FWHM, where q and FWHM are the peak position and full width at half maximum .…”

Ternary Blended Fullerene‐Free Polymer Solar Cells with 16.5% Efficiency Enabled with a Higher‐LUMO‐Level Acceptor to Improve Film Morphology

“…For the Y6 blends, the donor and nonfullerene acceptor perform perfect face‐on orientation as suggested by the (010) signal appearing mainly at the q z direction (around 1.75 Å −1 ) and the lamellar (100) signal seen at the q xy direction (around 0.29 Å −1 ). The additional peak at 0.425 Å −1 ( d ≈ 14.8 Å) in the in‐plane direction could be originated from the backbone ordering previously found in Y6 film . The scattering patterns of the PM6 and Y6 are well kept and the coherent crystalline length (CCL) of the π–π stacking (4.59 vs 4.77 nm) is maintained after the addition of 0.2 IDIC.…”

High‐Efficiency As‐Cast Organic Solar Cells Based on Acceptors with Steric Hindrance Induced Planar Terminal Group

“…[15,[26][27][28] So, the molecular conformation of the terminal region would directly influence the charge transport and the final photovoltaic performances. [15,[26][27][28] So, the molecular conformation of the terminal region would directly influence the charge transport and the final photovoltaic performances.…”