High-Efficiency and Stable Organic Solar Cells with Stacked LiF and Organic Electrolytes as Cathode Interface Layers

Abstract

The cathode interfacial layer plays a key role in enhancing the efficiency and stability of organic solar cells. Constructing efficient two-layer interfaces is one of the important strategies to improve device performance. In this work, we deposited a thin layer of lithium fluoride (LiF) beneath the electron transport layer poly[(9,9bis(3′-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9dioctylfluorene)]dibromide (PFN-Br) and (N,N-dimethyl-ammonium N-oxide)propyl perylene diimide (PDINO), respectively, to prepare conventional organic solar cells featuring a double electron transport layer. The V oc and FF of the optimized devices with a double electron transport layer were improved to achieve a power conversion efficiency (PCE) of 16.4% for LiF/PFN-Br-based devices and 16.0% for LiF/PDINObased devices. The LiF-containing double electron layers reduce the work function of the active layer, makes electron injection more efficient, and promotes charge extraction and collection. As an optical spacer layer, the thin layer of LiF also changes the internal light intensity distribution, enabling the active layer to absorb more photons and generate more excitons. In addition to PCE enhancement, the LiF-containing double layers still reduce photodegradation of the active layer and improve the stability of the device.

Hydrogen-bond-induced cathode engineering interface achieving high-efficiency organic solar cells

“…Evidently, the cells with 2N-SAM outperform those with bare ZnO in terms of their J SC , while their V OC and FF remain constant and are equivalent to those of conventional devices (ITO/PEDOT:PSS/PM6:Y6/L-PFN-Br/Ag). 41 We demonstrated that the higher J SC is due to the hydrogen bonds between Y6 and 2N-SAM, the better WF alignment between ZnO and Y6, and the better stratification in BHJ.…”

“…Evidently, the cells with 2N-SAM outperform those with bare ZnO in terms of their J SC , while their V OC and FF remain constant and are equivalent to those of conventional devices (ITO/PEDOT:PSS/PM6:Y6/L-PFN-Br/Ag). 41 We demonstrated Fig. 2 The FT-IR spectra of Y6, 2N-SAM and the 2N-SAM/Y6 (w/w, 1 : 1) blend.…”

Application of Buffer Layer to Improve the Efficiency of Organic Solar Cells

“…This knowledge can then be used to tailor and optimize materials to create more efficient and stable organic electronic devices. [123] Copyright 2021, American Chemical Society.…”

Organic–inorganic hybrid cathode interlayer materials for efficient organic solar cells

“…Consequently, PTB7:PC 71 BM based OSCs with TiO x /PEI gave a much increased PCE of 9.08%, compared to the 7.00% and 7.38% for those with individual PEI or TiO x as the ETL, respectively. Jiang and Fang et al employed a fullerene derivative C60 pyrrolidine tris-acid 113 The LiF layer was deposited by vacuum evaporation with ca. 1 nm thickness, which can act as the optical spacer layer to optimize the light intensity distribution resulting in better light harvesting.…”

“…Recently, Yang and Zhao et al reported a kind of double layer CIL of LiF/PFNBr or LiF/PDINO in conventional OSCs. 113 The LiF layer was deposited by vacuum evaporation with ca. 1 nm thickness, which can act as the optical spacer layer to optimize the light intensity distribution resulting in better light harvesting.…”