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2D Ruddlesden–Popper perovskites (RPPs) are emerging as potential challengers to their 3D counterpart due to superior stability and competitive efficiency. However, the fundamental questions on energetics of the 2D RPPs are not well understood. Here, the energetics at (PEA)2(MA)n−1PbnI3n+1/[6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) interfaces with varying n values of 1, 3, 5, 40, and ∞ are systematically investigated. It is found that n–n junctions form at the 2D RPP interfaces (n = 3, 5, and 40), instead of p–n junctions in the pure 2D and 3D scenarios (n = 1 and ∞). The potential gradient across phenethylammonium iodide ligands that significantly decreases surface work function, promotes separation of the photogenerated charge carriers with electron transferring from perovskite crystal to ligand at the interface, reducing charge recombination, which contributes to the smallest energy loss and the highest open‐circuit voltage (Voc) in the perovskite solar cells (PSCs) based on the 2D RPP (n = 5)/PCBM. The mechanism is further verified by inserting a thin 2D RPP capping layer between pure 3D perovskite and PCBM in PSCs, causing the Voc to evidently increase by 94 mV. Capacitance–voltage measurements with Mott–Schottky analysis demonstrate that such Voc improvement is attributed to the enhanced potential at the interface.

Ternary architecture is a promising strategy to enhance power conversion efficiencies (PCEs) of organic solar cells (OSCs). However, among all the photovoltaic parameters that govern the final PCEs, the fill factor (FF) for ternary OSCs is generally below 78%, limiting solar cells’ performance. Here, charge dynamics in the ternary cells PM6:DRTB‐T‐C4:Y6 with a FF of 80.88% and a PCE of 17.05% are thoroughly investigated by a series of transient characterization technologies, including transient absorption spectroscopy, transient photovoltage, and transient photocurrent measurements. The impressive FF results from effective exciton dissociation, enhanced charge transport and suppressed recombination in ternary cells. Moreover, the correlation between the measured FF and the charge recombination‐extraction competition is quantitatively analyzed by using a circuit model. The ternary cells also show small energy loss (Eloss). The findings here provide insight into achieving high‐FF and low‐Eloss ternary OSCs.

Ternary architecture is an efficient strategy to boost desired power conversion efficiency of single-junction organic solar cells (OSCs). Here, a ternary OSC by incorporating a compatible acceptor ITIC-M as a third component into state-of-the-art PM6:Y6 blend is reported, yielding a power conversion efficiency of 18.13% and an impressive fill factor of 80.10%. The efficiency is the highest record for the PM6:Y6 based ternary devices reported to date. The full advantages of the designed ternary heterojunction are the good complementary light absorption that increases the photocurrent, and the matched interfacial electronic structures featuring so-called pinning energies that facilitate exciton separation and suppress charge recombination loss. Furthermore, ITIC-M plays a vital role in optimizing the micromorphology of the ternary blend with better dispersity, well-formed fibrillar structure and enhanced crystallinity, thus boosting the charge transport and device performance.

In article number 2000687, Qinye Bao and co‐workers systematically investigate the energetics and energy loss in 2D Ruddlesden‐Popper perovskite (RPP) solar cells. The crucial scenario found at the 2D RPP/electron transport layer interface is that the potential gradient across ligands promotes separation of the photogenerated carrier, with electrons transferring from the perovskite crystal to the electron transport layer.

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