19.32% Efficiency Polymer Solar Cells Enabled by Fine‐Tuning Stacking Modes of Y‐Type Molecule Acceptors: Synergistic Bromine and Fluorine Substitution of the End Groups

Abstract

The success of Y6‐type nonfullerene small molecule acceptors (NF‐SMAs) in polymer solar cells (PSCs) can be attributed to their unique honeycomb stacking style, which leads to favorable thin‐film morphologies. The intermolecular interactions related to the crystallization tendency of these NF‐SMAs is closely governed by their electron accepting end groups. For example, the high performance Y6 derivative L8‐BO (BTP‐4F) presents three types of stacking modes in contrast to two stacking modes of Y6. Hence, it is ultimately interesting to obtain more insight on the packing properties and the preferences influenced by chemical modifications such as end group engineering. This work designs and synthesizes asymmetric and symmetric L8‐BO derivatives with brominated end groups and explores the stacking preferences in various modes. The asymmetric BTP‐3FBr displays an optimized crystallization tendency and thin film morphology, leading to a decent power conversion efficiency (PCE) of 18.34% in binary devices and a top PCE of 19.32% in ternary devices containing 15 wt% IDIC as the second acceptor.

Quinoxaline-based nonfullerene acceptors with powerful core-functionalization ability enabling efficient solar energy utilization

“…Compared to fluorine and chlorine atoms, bromine atoms present a large and loose electron cloud, which is favorable for polarization and forming enhanced intermolecular packing. 130–134 CH-series acceptors (CH-20, CH-21, and CH-22) are prepared by stepwise bromination on the core. 62 In Fig.…”

Multifunctional PMMA intermediate layer for sequentially deposited organic photovoltaics

“…Over the past decade, organic photovoltaics (OPVs) have garnered significant interest due to their attractive features such as solution processability, low cost, and eco-friendliness. 1–22 Within OPVs, excitons (excitation states generated by the absorption of sunlight) migrate to the donor–acceptor interface, where they give rise to charge-transfer states, which can then dissociate into free charge carriers: holes and electrons. These charge carriers are transported through phases rich in donor and acceptor materials, respectively, culminating at the electrodes where they are harvested.…”

Polythiophene and its derivatives for all-polymer solar cells

“…9–18 The power conversion efficiency (PCE) of high-performance OSCs is rapidly exceeding 20%, propelled by breakthroughs in molecular design and device optimization. 19–24 However, these high-performance materials typically feature complex chemical structures and involve complicated synthesis steps, leading to high costs. 25 Moreover, the inherent difficulties in scaling up may constrain their future practical applications.…”