A Polycrystalline Polymer Donor as Pre‐Aggregate toward Ordered Molecular Aggregation for 19.3% Efficiency Binary Organic Solar Cells

Abstract

Organic semiconductors are generally featured with low structure order in solid state films, which leads to low charge transport mobility and strong charge recombination in their photovoltaic devices. In this work, we report a “polycrystal‐induced aggregation” strategy to order the polymer donor (PM6) and non‐fullerene acceptor (L8‐BO) molecules during solution casting with the assistance of PM6 polycrystals that were incubated through a vapor diffusion method, toward improved solar cell efficiency with either thin or thick photoactive layers. These PM6 polycrystals were redissolved in chloroform to prepare PM6 pre‐aggregates (PM6‐PA), and further incorporated into the conventional PM6:L8‐BO blend solutions, which was found to prolong the molecular organization process and enhance the aggregation of both PM6 and L8‐BO components. As the results, with the assistance of 10% PM6‐PA, PM6:L8‐BO solar cell devices obtained power conversion efficiencies (PCEs) from 18.0% and 16.2% to 19.3% and 17.2% with a 100 and 300 nm ‐thick photoactive layer respectively.This article is protected by copyright. All rights reserved

Light-induced quinone conformation of polymer donors toward 19.9% efficiency organic solar cells

“…3a and b, the reference PM6:L8-BO film shows a (100) diffraction peak at q z = 0.30 Å −1 and a (010) π–π stacking crescent at q z = 1.73 Å −1 , consistent with previous work. 28 Upon UV-light treatment, pronounced enhancements are observed for both the (100) and (010) peaks, suggesting that the impact of the quinone-conformation in enhancing the structural order of PM6 is still effective with the presence of L8-BO. The D18:L8-BO film presents a similar GIWAXS pattern evolution upon UV light treatment, confirming the versatility of the blend film (Fig.…”

“…25–27 Modulating the self-assembly behavior of photovoltaic materials during film formation via controlling the solution state has been considered as a facile and easy-to-process method, and has attracted extensive interest very recently. 28–30 For example, the replacement of a “poor solvent” with a “good solvent” can lead polymers to exhibit strong intrinsic preaggregation and further improve their domain size and purity after film-formation, thus facilitating efficient charge transport in their photovoltaic films. 31 Temperature-dependent aggregation properties can also give polymers different aggregation behavior in the solution-state and allow them to organize into distinct molecular order in solid films.…”

π-Extended Nonfullerene Acceptor for Compressed Molecular Packing in Organic Solar Cells To Achieve over 20% Efficiency

“…In situ spectroscopic ellipsometry (SE) measurements of the molecular aggregation dynamics of NFA films (experiment details described in the Supporting Information) depicted in Figures S3 and S4 show that the aggregation of L8-BO molecules began earlier (1.4s) than that of pure film (1.7s) with the presence of B6Cl, therefore extends the total molecular organization time to enhance crystallinity, and consequently increases the extinction coefficient . Meanwhile, from the 1D grazing incidence small-angle X-ray scattering (GISAXS) profiles of L8-BO, B6Cl, and L8-BO:B6Cl blend films, a “shoulder” at q xy = 0.01 Å –1 (associated with enlarged fractal dimension) shows up in the 1D GISAXS profiles (Figure S5), validating the strong aggregation in the blend film as we discussed above.…”

“…Modulating the molecular packing of photovoltaic materials has been widely accepted as a crucial way to resolve the above issues. However, although extensive chemical and physical approaches have been dedicated to enhancing the molecular order of OPVs to enhance light absorption and charge transport, − strongly increased nonradiative energy loss has also been routinely observed in the literature, , which can be attributed to the suppressed luminescence due to increased intermolecular aggregation. Regarding that, the primary obstacle to the further PCE development in OPVs lies in the striking balance between aggregation and luminescent efficiency, − and therefore it has been well considered as a grand challenge to eliminate the trade-off between J SC and V OC.…”

Alkoxythiophene‐Directed Fibrillization of Polymer Donor for Efficient Organic Solar Cells

“…The TRPL data were fitted with a double exponential model in which the longer decay time represents the crystalline region and the shorter one can be ascribed to the amorphous region. [35] As shown in Figure S3a Then MD simulations were conducted to validate how these alkoxythiophene additives affect the intermolecular interaction of PM6, where an adsorption module was utilized using PM6 molecule containing five repeating units as the substrate and four additive molecules as the adsorbates. As illustrated in Figure 2a-c, T-2OMe tends to adsorb on the conjugated backbone of PM6.…”