Facile Synthesis of Polycyclic Aromatic Hydrocarbon (PAH)–Based Acceptors with Fine‐Tuned Optoelectronic Properties: Toward Efficient Additive‐Free Nonfullerene Organic Solar Cells

Abstract

A series of polycyclic aromatic hydrocarbons (PAHs) with extended π‐conjugated cores (from naphthalene, anthracene, pyrene, to perylene) are incorporated into nonfullerene acceptors for the first time. Four different fused‐ring electron acceptors (FREAs), i.e., DTN‐IC‐2Ph, DTA‐IC‐3Ph, DTP‐IC‐4Ph, and DTPy‐IC‐5Ph, are prepared via simple and facile synthetic procedures, yielding a remarkable platform to study the structure–property relationship for nonfullerene solar cells. With the PAH core being extended systematically, the gradually redshifted absorption with enhanced molar extinction coefficient (ε) is realized, the energy level of the highest occupied molecular orbital is up‐shifted, and the electron mobility is greatly enhanced. Meanwhile, the solubility decreases and the molecular packing becomes strengthened. As a result, with an optimized combination of these characteristics, DTP‐IC‐4Ph attains good solubility, high molar extinction coefficient, complementary absorption, suitable morphology, well‐matched energy levels, as well as efficient charge dissociation and transport in blend film. Consequently, the DTP‐IC‐4Ph‐based solar cells with a donor polymer, poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PBDB‐T) exhibit a promising power conversion efficiency of 10.37% without any additives, which is close to the best performance achieved in additive‐free nonfullerene solar cells (NFSCs). The results demonstrate that the PAH building blocks have great potential for the construction of novel FREAs for efficient additive‐free NFSCs.

Additive‐Free Non‐Fullerene Organic Solar Cells

“…firstly introduced a series of polycyclic aromatic hydrocarbons (PAHs) into NFSMAs and developed four acceptors (DTP‐IC‐xPh) through a simple and low‐cost synthetic route. With good solubility, matching energy level and complementary absorption to the acceptor PDBD‐T, the DTP‐IC‐4Ph‐based ( 3.7 ) additive‐free OSCs attained a PCE of 10.37 % with a V OC of 0.900 V, a J SC of 17.32 mA cm −2 and a FF of 66.6 % . It should be noted that the DTP‐IC‐4Ph can be readily accessed from the low‐cost commercial starting material 1,6‐dibromopyrene via Stille coupling reaction, followed by lithiation and ring‐closure reaction.…”

The role of connectivity in significant bandgap narrowing for fused-pyrene based non-fullerene acceptors toward high-efficiency organic solar cells

“…Another two NFAs with the pyrene core connecting with end groups via 2,9-positions named Py-1 and Py-2 also exhibited a wide bandgap of 1.95 and 1.97 eV respectively, leading to low J SC and PCE. 33 On the other hand, "DTP-IC-4Ph" (dithieno[f-g,m-n](di(para-hexyl) phenyl)cyclohexapyrene-IC) from Guo et al 34 with the pyrene core connecting with end groups via 1,8-positions presented a notably red-shied absorption spectrum and thus a clearly improved J SC of 17.32 mA cm À2 and PCE of 10.37%. However, the reasons for the red-shied spectra and how the connection position of the pyrene core can inuence the properties of the resulting molecules have not been systematically studied.…”

A Novel Carbazole‐Based Nonfullerene Acceptor for High‐Efficiency Polymer Solar Cells

“…Meanwhile, the D core also plays a key role in adjusting the s and energy levels of NFAs. For example, using a strong electron‐donating capacity D core can amplify the intramolecular charge transfer (ICT) effect for a narrow . However, such a D core also leads to a high HOMO level, which not only astrict the option of donor material but also limit the increase in V oc .…”