Impact of Sequential Fluorination of Donor and/or Acceptor Polymers on the Efficiency and Morphology of All-Polymer Solar Cells

Abstract

To fine-tune all-polymer solar cells (all-PSCs), fluorine atoms were introduced on the bithiophene of thiophene-flanked dioxo-benzodithiophene-based donor polymers (P2T-0F and P2T-2F) and/or on the bithiophene of naphthalenediimide (NDI)-based acceptor polymers (NDI-0F and NDI-2F). The resultant four combinations [P2T-0F:NDI-0F (or NDI-2F) and P2T-2F:NDI-0F (or NDI-2F)] exhibited dramatically different morphologies, surface free energies (polar and dispersion components), and electrical properties, largely reflected in their power conversion efficiencies (PCEs). Notably, the highest PCE (3.28%, P2T-2F:NDI-0F blend) correlated with the polar components of the surface free energies of the donor and acceptor polymers and improved charge transport properties. The other fluorinated (P2T-0F:NDI-2F and P2T-2F:NDI-2F) and non-fluorinated (P2T-0F:NDI-0F) blends exhibited lower PCE values owing to their poor miscibility and edge-on-rich orientation. We demonstrate a delicate but significant impact of sequential fluorination on the studied polymer blends, which is informative for key structure−property relationships of all-PSCs.

Donor Functionalization Tuning the N‐Type Performance of Donor–Acceptor Copolymers for Aqueous‐Based Electrochemical Devices

“…The gNDI-FBT presented deeper lying E LUMO and E HOMO with respect to gNDI-EDBT and gNDI-BT, resulting from the strong electron-withdrawing character of fluorine atom on donor. [28,49] Furthermore, the deep E LUMO would promote electron injection and improve gNDI-FBT potential stability window in aqueous media. [28] In addition, gNDI-FBT and gNDI-BT have low-lying LUMO (<−4.02 eV), which are favorable energetics of ion bulk doping into the semiconducting polymers.…”

Diketopyrrolopyrrole-Based Chlorinated Bithiophene Polymers for Organic Solar Cells: Effect of Thiophene or Pyridine Flank

“…Interestingly, the smallest |ΔSFE d+p | between DPP2ThCl and Y6 yielded the highest PCE. However, the PCE versus |ΔSFE| did not show a general correlation among all of the plots as was the case in previous reports . The χ parameters between the donor and acceptor components were also calculated from the SFE, , which exhibited a plot similar with that of |ΔSFE| (Figure d and Figure S19).…”

“…However, the PCE versus |ΔSFE| did not show a general correlation among all of the plots as was the case in previous reports. 66 The χ parameters between the donor and acceptor components were also calculated from the SFE, 66,69 which exhibited a plot similar with that of |ΔSFE| (Figure 5d and Figure S19). Accordingly, the highest PCE of DPP2ThCl:Y6 is explained by the good miscibility of donors and acceptors (AFM and small |ΔSFE d+p |), a better crystallinity of NFA in the blend (2D-GIXRD), an improved hole mobility and hole/electron mobility balance (SCLC), and a narrow E g value for Y6.…”

“…In addition to the morphological and charge transport characterizations, we performed CA (Figure S18 and Table S5) measurements for both donor and acceptor materials to analyze their SFE and χ parameters. − The CA and SFE values of donors and acceptors and χ values between the donors and acceptors are summarized in Tables S5 and S6, respectively. We then plotted the PCE versus the absolute difference of the total SFE (|ΔSFE d+p |), the polar component (|ΔSFE p |), and dispersion component (|ΔSFE d |), as shown in Figure a–c, respectively.…”

Improved Predictions of Organic Photovoltaic Performance through Machine Learning Models Empowered by Artificially Generated Failure Data

“…However, no general consistency was observed in the differences in total SFE, or its polar and dispersion components; previous reports would indicate that small differences in SFE between donor and acceptor polymers yields favorable mixing and high PCE. 54 The number-averaged molecular weight (M n ) and polydispersity index of P3 were moderate (8.8−24.9 kg mol −1 and 1.8− 2.7, respectively: Table 1) and did not correlate with the device PCEs. Accordingly, crystallinity, polymer orientation, molecular weight, and SFE alone cannot be correlated with PCE exptl .…”