Thick‐Film Organic Solar Cells Achieving over 11% Efficiency and Nearly 70% Fill Factor at Thickness over 400 nm

Abstract

Thickness‐insensitive small molecule acceptors (SMAs) are still a great challenge for developing thick‐film organic solar cells (OSCs) towards practical use. Herein, two SMAs, MF1 and MF2, are designed and synthesized by employing a bifunctional end group with fluorine and methyl moieties. Combined with fused‐ring cores with alkyl side chains, both MF1 and MF2 exhibit ordered π–π stacking and high charge carrier mobilities in neat and blend films. The champion devices based on PM7:MF1 and PM7:MF2 deliver high power conversion efficiencies (PCEs) of 12.4% and 13.7%, and high fill factors (FFs) of 78.3% and 74.5%, respectively. With increasing active layer thickness, the FFs of the OSCs decrease relatively slowly, demonstrating the preferrable properties of MF1 and MF2 in terms of their thickness insensitivity, especially for MF1. As a result, the two thick‐film OSCs achieve over 11% PCEs at an active layer thickness over 400 nm (an FF close to 70% for PM7:MF1) and over 10% PCEs when the thickness is increased up to 500 nm. These are the highest PCEs among OSCs with such active layer thicknesses to date. This work reveals a molecular design strategy by reasonably combining fluorine and methyl together to simultaneously enhance charge carrier mobilities and fine‐tune the morphology, which is beneficial to achieve high‐performance thick‐film OSCs.

Effect of 4-biphenyl groups on the charge transport and photovoltaic properties of arylamine based push–pull systems

“…While it is indeed well established that the use of additional hole transporting layers (BPAPF) and extraction/injection barriers (BPAPF doped with NDP9/NDP9) has a beneficial effect on the FF, such values, amongst the highest reported so far, 19,31 have been barely achieved in all-small molecule OSCs. [32][33][34][35][36] The characterization of PHJ cells fabricated by thermal evaporation has revealed very high FF values consistent with the high hole mobilities measured for the donor materials.…”

Over 15.7% Efficiency of Ternary Organic Solar Cells by Employing Two Compatible Acceptors with Similar LUMO Levels

“…In this work, a series of OSCs were fabricated by using polymer material PM6 as donor and non‐fullerene materials IPTBO‐4Cl, [ 23 ] MF1, [ 24 ] and their blend as acceptor. The schematic diagram of OSCs and the chemical structures of PM6, IPTBO‐4Cl, and MF1 are shown in Figure a.…”

Influences of Quinoid Structures on Stability and Photovoltaic Performance of Nonfullerene Acceptors

“…[ 22–25 ] These properties bring about benefits in good photovoltaic performances and thickness insensitivity for polymer donors. [ 26–29 ] Very recently, via the adoption of the strong quinoid units as the cores, a new family of small‐molecule nonfullerene acceptors (NFAs), known as Y‐series NFAs, has been reported to have high electron mobility, a broad absorption region, and low energy loss. [ 30–35 ] The power conversion efficiencies (PCEs) of Y‐series NFA–based OSCs have been boosted to over 17% by material optimization, [ 36–38 ] or using ternary blends.…”