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A series of new small-molecule acceptors—NA9, NA10, and NA11—based on benzo[b]phenazine are synthesized. The chlorinated NA10 and brominated NA11 exhibit improved molecular packing and enhanced charge transport, resulting in higher power conversion efficiencies (PCEs) of 15.65% and 16.64%, respectively, compared to 11.66% for the non-halogenated NA9. These results underscore the great potential of peripheral halogenation particularly bromination, in achieving high-performance OSCs. [ABSTRACT FROM AUTHOR]

The ternary strategy has proven effective in enhancing the performance of organic solar cells (OSCs), yet identifying the optimal third component remains a challenge due to the lack of theoretical frameworks for predicting its impact based on molecular structure. This study addresses this challenge by proposing quantitative parameters derived from molecular surface electrostatic potential (ESP) as criteria for selecting ternary components. The asymmetric acceptor BTP‐OS, which exhibits a lower total average ESP and larger molecular polarization index relative to the host acceptor, is introduced into the PM6:L8‐BO system. This incorporation led to weakened ESP‐induced intermolecular interactions and reduce miscibility with donor polymer, resulting in an optimized multi‐scale morphology of the ternary blend. Consequently, the ternary device achieved an efficiency of 19.72%, one of the highest values for PM6:L8‐BO‐based ternary devices, with enhanced exciton dissociation and charge collection, lower energy disorder, and minimized non‐radiative energy losses. Comparable efficiency improvements are also verified in PM6:BTP‐eC9 and D18:N3 systems, demonstrating the broad applicability of the proposed approach. This study not only provides a practical and effective principle for selecting ternary components but also establishes a broader framework for optimizing ternary OSCs, potentially advancing the development of more efficient OSCs across diverse material systems. [ABSTRACT FROM AUTHOR]

Carbazole-based self-assembled monolayer (SAM) materials as hole transport layers (HTL) have led organic solar cells (OSCs) to state-of-the-art photovoltaic performance. Nonetheless, the impact of the alkyl spacer length of SAMs remains inadequately understood. To improve the knowledge, four dichloride-substituted carbazole-based SAMs (from 2Cl-2PACz to 2Cl-5PACz) with spacer lengths of 2-5 carbon atoms is developed. Single crystal analyses reveal that SAMs with shorter spacers exhibit stronger intermolecular interactions and denser packing. The molecular conformation of SAMs significantly impacts their molecular footprint and coverage on ITO. These factors result in the highest coverage of 2Cl-2PACz and the lowest coverage for 2Cl-3PACz on ITO. OSCs based on PM6:L8-BO with 2Cl-2PACz as HTL achieved high efficiencies of 18.95% and 18.62% with and without methanol rinsing of the ITO/SAMs anodes, corresponding to monolayer and multilayer structures, respectively. In contrast, OSCs utilizing the other SAMs showed decreased efficiencies as spacer length increased. The superior performance of 2Cl-2PACz can be attributed to its shorter spacer, which reduces series resistance, hole tunneling distance, and barrier. This work provides valuable insights into the design of SAMs for high-performance OSCs., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Trap-assisted charge recombination is one of the primary limitations of restricting the performance of organic solar cells. However, effectively reducing the presence of traps in the photoactive layer remains challenging. Herein, wide bandgap polymer donor PTzBI-dF is demonstrated as an effective modulator for enhancing the crystallinity of the bulk heterojunction active layers composed of D18 derivatives blended with Y6, leading to dense and ordered molecular packings, and thus, improves photoluminescence quenching properties. As a result, the photovoltaic devices exhibit reduced trap-assisted charge recombination losses, achieving an optimized power conversion efficiency of over 19%. Besides the efficiency enhancement, the devices comprised of PTzBI-dF as a third component simultaneously attain decreased current leakage, improved charge carrier mobilities, and suppressed bimolecular charge recombination, leading to reduced energy losses. The advanced crystalline structures induced by PTzBI-dF and its characteristics, such as well-aligned energy level, and complementary absorption spectra, are ascribed to the promising performance improvements. Our findings suggest that donor phase engineering is a feasible approach to tuning the molecular packings in the active layer, providing guidelines for designing effective morphology modulators for high-performance organic solar cells., Competing Interests: Declarations. Conflict of interest: The authors declare no interest conflict. They have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024. The Author(s).)