Asymmetric Acceptors Enabling Organic Solar Cells to Achieve an over 17% Efficiency: Conformation Effects on Regulating Molecular Properties and Suppressing Nonradiative Energy Loss

Abstract

Y6, as a state‐of‐the‐art nonfullerene acceptor (NFA), is extensively optimized by modifying its side chains and terminal groups. However, the conformation effects on molecular properties and photovoltaic performance of Y6 and its derivatives have not yet been systematically studied. Herein, three Y6 analogs, namely, BP4T‐4F, BP5T‐4F, and ABP4T‐4F, are designed and synthesized. Owing to the asymmetric molecular design strategies, three representative molecular conformations for Y6‐type NFAs are obtained through regulating the lateral thiophene orientation of the fused core. It is found that conformation adjustment imposes comprehensive effects on the molecular properties in neat and blend films of these NFAs. As a result, organic solar cells (OSCs) fabricated with PM6:BP4T‐4F, PM6:BP5T‐4F, and PM6:ABP4T‐4F show high power conversion efficiency of 17.1%, 16.7%, and 15.2%, respectively. Interestingly, these NFAs with different conformations also show reduced energy loss (Eloss) in devices via gradually suppressed nonradiative Eloss. Moreover, by employing a selenium‐containing analog, CH1007, as the complementary third component, ternary OSCs based on PM6:BP5T‐4F:CH1007 (1:1.02:0.18) achieve a 17.2% efficiency. This work helps shed light on engineering the molecular conformation of NFAs to achieve high efficiency OSCs with reduced voltage loss.

Hybrid Perovskite Quantum Dot/Non‐Fullerene Molecule Solar Cells with Efficiency Over 15%

“…During the past five years, the development of narrow optical bandgap non‐fullerene electron acceptors (NFAs) like Y6 further extends the solar response spectrum of organic solar cells and PCEs above 16% has been widely demonstrated. [ 23–25 ] Concurrently, CsPbX 3 (X = Cl − , Br − , I − , or mixed‐halide) QDs with all‐inorganic crystal structures have emerged as a rising star for optoelectronic applications because of their stronger flexibility in adjusting the composition, optical and electrical properties, high photoluminescence quantum yields (PLQYs) due to impressive defect tolerance. Advances in CsPbI 3 QD solar cells have enabled high efficiency over 14%, [ 26–31 ] showing great potential for QD PVs.…”

A Synergistic Strategy of Manipulating the Number of Selenophene Units and Dissymmetric Central Core of Small Molecular Acceptors Enables Polymer Solar Cells with 17.5 % Efficiency

“…The best FF for PM6 : A‐WSSe‐Cl may be ascribed to the dissymmetric structure feature and the most favorable morphology. To the best of our knowledge, the remarkably PCE of 17.51 % for A‐WSSe‐Cl is the highest value for the dissymmetric non‐fullerene SMAs‐based binary PSCs and also the highest values for the reported selenophene‐based SMAs binary PSCs (see Chart S1–2, Table S5–6) [15–17, 19a, 25, 30–32, 39] . Such results indicate our synergistic strategy of selenophene‐containing and dissymmetrical core not only can achieve an impressive FF, but also can present a high J sc , thereby obtaining an impressive efficiency.…”

“…Among them, the popular strategies for modification of central core include π‐conjugated length extension strategy, [18] dissymmetric backbone strategy, [19] and subunit replacement strategy, [20, 21] which show the great potential in adjusting the optoelectrical properties and enhancing PCE. For example, currently, a series of high‐performance NF‐SMAs based on dissymmetric DAD central cores have been developed, which achieved an improved intermolecular stacking and an optimized morphology of the blend films, led to promoting the FF of PSCs in comparison with that of their symmetric counterparts [22–25] . However, the relatively lower J sc in most reported cases were observed might due to their relatively wider optical band gap and unfavorable molecular conformation, thus the trade‐off among device parameters is still quite difficult to achieve in dissymmetric DAD central core‐based NF‐SMAs.…”

Comparing and Quantifying Indoor Performance of Organic Solar Cells

“…Straight lines exhibit the maximum Shockley-Queisser efficiencies for the different input LED spectra. Dashed lines incorporate an additional, non-radiative voltage loss of 180 meV representative of the lowest reported values in the literature that are in the range of 0.16-0.2 V. [88,92,93] For the samples, which reached the best efficiencies with the 2700 K LED of Cui et al, the peak around 1.84 eV is overlapping with the position of the Shockley-Queisser maximum, suggesting the band gap to be suitable for this LED illumination. Theoretically, with this kind of LED spectrum a maximum efficiency of 54% is possible, emphasizing the potential for further improvements.…”