Miscibility-Driven Optimization of Nanostructures in Ternary Organic Solar Cells Using Non-fullerene Acceptors

Abstract

Non-fullerene acceptors (NFAs) with vibrant superiority over fullerene derivatives have proved advantageous as a guest component in a ternary blend signifying improved photon harvesting. However, heterogeneity of NFA-based ternary blend morphology is very complex, and the optimization requires simultaneous considerations of molecular miscibility and electronic properties. We discuss the role of guest NFA for an eased optimization of ternary blend photoactive layer in four different ways. Our four-model prospect of component selection is driven by the well-matched intrinsic miscibility, electronic, and optical characteristics of organic materials. We analyze each model, modulating photoactive layer morphology toward efficient transfer, transport, and collection of charges along with their balanced dissociation and drifting. We believe a model-based selection of NFA and its organization as a guest in a complex ternary blend will serve as a guide for researchers to optimize thin film nanostructures, a route toward efficient larger-area ternary devices.

Over 12% Efficiency Nonfullerene All‐Small‐Molecule Organic Solar Cells with Sequentially Evolved Multilength Scale Morphologies

“…In out‐of‐plane profile, a diffraction peak at 1.83 Å −1 can be seen in high‐q region. Thus ZnP‐TBO is more readily to order upon spin‐coating and 6TIC is mostly dissolved or kinetically trapped in mixture (associated with TEM and RSOXS results) . We have seen previously that DPP‐porphyrin molecule family is quite immiscible with PCBM, and such a difference in NFSM system indicates the necessity of different optimization avenues.…”

Energetic Disorder and Activation Energy in Efficient Ternary Organic Solar Cells with Nonfullerene Acceptor Eh‐IDTBR as the Third Component

“…Compared with the binary device of PCE10:F8IC, the parameters of V OC , J SC , and FF indeed were improved. Especially, we found a clear increase in the EQE in the wavelength range from 500 to 900 nm (Figure b), and the enhancement was attributed to improved charge transfer efficiency in the optimized ternary blend due to more mixed donor/acceptor phases with larger interfacial areas when ≈18 wt% Eh‐IDTBR was added to the active layer . We also briefly analyzed the charge carrier recombination qualitatively by checking J SC and V OC under various illumination light intensities (Figure c,d).…”

“…Thus, E CT of 1.07 and 1.02 eV for the optimized devices of ternary and PCE10:F8IC were obtained, whereas 0.87 and 0.82 eV were determined from the intercept with the Y ‐axis for the optimized devices of ternary and PCE10:F8IC. Upon adding Eh‐IDTBR in the active layer to form a ternary mixture, we see that E CT was not affected dramatically, and it was attributed to the good miscibility of Eh‐IDTBR with both PCE10 and F8IC, as shown by atomic force microscopy (AFM) (Figure S5, Supporting Information) and transmission electron microscopy (TEM) (Figure S6, Supporting Information) …”

Critical Role of Polymer Aggregation and Miscibility in Nonfullerene‐Based Organic Photovoltaics

“…[11] The origin of this difference may be related to the different aggregation properties between fullerene and IDTBR as well as the different miscibility between polymers and acceptors. [23,24,42] The apparent peak shoulder in the high q region shown in T4T and PffBT4T 90 -co-3T 10 profiles suggests the multiscale morphologies with different-sized domains, indicating different film-formation processes involved.…”

“…[18][19][20] Favorable donor-acceptor miscibility helps phase separation occur at appropriate length-scales during de-mixing of the blend component as the solvent evaporates. [21,22] Compared to fullerene molecules, the NFAs have shown many different physicochemical properties, such as high miscibility with donor polymers due to similar surface energy [23,24] and strong π-π interactions formed by electron-deficient end-capping units. [25] Thus, the development of new donor polymers matching the properties of NFAs requires a new understanding of the formation of the polymer-NFA photoactive blend.…”