Precise Control of Selenium Functionalization in Non‐Fullerene Acceptors Enabling High‐Efficiency Organic Solar Cells

Abstract

Central π-core engineering of non-fullerene small molecule acceptors (NF-SMAs) is effective in boosting the performance of organic solar cells (OSCs). Especially, selenium (Se) functionalization of NF-SMAs is considered a promising strategy but the structureperformance relationship remains unclear. Here, we synthesize two isomeric alkylphenyl-substituted selenopheno[3,2-b]thiophene-based NF-SMAs named mPh4F-TS and mPh4F-ST with different substitution positions, and contrast them with the thieno[3,2b]thiophene-based analogue, mPh4F-TT. When placing Se atoms at the outer positions of the π-core, mPh4F-TS shows the most red-shifted absorption and compact molecular stacking. The PM6 : mPh4F-TS devices exhibit excellent absorption, high charge carrier mobility, and reduced energy loss. Consequently, PM6 : mPh4F-TS achieves more balanced photovoltaic parameters and yields an efficiency of 18.05 %, which highlights that precisely manipulating selenium functionalization is a practicable way toward high-efficiency OSCs.

Fine-Tuning of Polymer Aggregation Properties via Regulating the Side Chain Arrangement for Efficient Organic Solar Cells

“…Organic solar cells (OSCs) based on a polymer or small molecule material as the electron donor blended with either a fullerene/nonfullerene acceptor as the electron-accepting material have attracted considerable research attention due to their unique advantages such as mechanical flexibility, semitransparency, and low-cost fabrication technologies. − To date, a great amount of research effort in the area of OSCs has been focused on developing various ladder-type nonfullerene small molecular acceptors (SMAs). − The power conversion efficiencies (PCEs) over 18% have been achieved by the combined research efforts of morphology control, interface engineering, and device optimization. − It is noted that most of the high-efficiency OSCs are usually processed from environmentally hazardous halogenated hydrocarbons including chloroform, chlorobenzene, etc., − which significantly restricted the commercial viability of this technology . In addition, processing additives were typically employed to optimize the thin film morphology and thus device performance, which made the device fabrication process even more complicated. − Therefore, it is highly demanded to design and synthesize high-performance materials with a simple fabrication process without using toxic chlorinated solvents for large-scale applications of OSCs.…”

Meta-Analysis of Molecular Design Strategies for Non-Fullerene Acceptor Based Organic Solar Cell Materials

“…Selenium has been shown to have multiple advantages over sulfur and has a high promise in NFAs. 29,[32][33][34][35][36][37] Due to the increased polarizability of selenium, the looser outermost electrons can overlap more with orbitals from neighboring π-conjugated units. This can lead to a stronger quinoidal character and improve the molecular planarity by the stronger non-covalent interactions "locking" the conformation and reducing rotations.…”

Manipulation and Direct Characterization of Polymer/Small-Molecule Interface Morphology in Bulk-Heterojunction Solar Cell

“…The device performance of organic photovoltaics (OPVs) has improved remarkably owing to the recent development of novel light-harvesting materials. − Nonfullerene structured acceptors (NFAs) such as ITIC and Y6, employed as n -type materials in OPVs, provide complementary absorption with p -type conjugated polymers (CPs) and enable one to maximize light-harvesting capabilities and enhance the power conversion efficiency (PCE). − The efficacy of NFAs is more pronounced in OPVs with a bulk-heterojunction (BHJ) architecture where NFA ( n -types) and CP ( p -types) are intermixed at a nanoscale. , Therefore, the development and application of new NFAs are of interest to further improve the OPV performance. Because NFAs are adopted as electron acceptors in BHJ OPVs, their working mechanism is the same as that of fullerene derivatives. , This indicates that managing the film morphology composed of CPs and NFAs, such as the interfacial area, domain size, and crystallinity of individual domains, has a decisive effect on the OPV performance. , Therefore, understanding the interface properties between CPs and NFAs is essential for devising efficient light-harvesting materials for BHJ-type OPVs.…”