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For organic solar cells to be competitive, the light-absorbing molecules should simultaneously satisfy multiple key requirements, including weak-absorption charge transfer state, high dielectric constant, suitable surface energy, proper crystallinity, etc. However, the systematic design rule in molecules to achieve the abovementioned goals is rarely studied. In this work, guided by theoretical calculation, we present a rational design of non-fullerene acceptor o-BTP-eC9, with distinct photoelectric properties compared to benchmark BTP-eC9. o-BTP-eC9 based device has uplifted charge transfer state, therefore significantly reducing the energy loss by 41 meV and showing excellent power conversion efficiency of 18.7%. Moreover, the new guest acceptor o-BTP-eC9 has excellent miscibility, crystallinity, and energy level compatibility with BTP-eC9, which enables an efficiency of 19.9% (19.5% certified) in PM6:BTP-C9:o-BTP-eC9 based ternary system with enhanced operational stability.

Anode interlayers play critical roles in organic solar cells, impacting the electrode's work function, energy level alignment, hole extraction, and electrode surfaces. However, the development of the commonly used anode interlayer PEDOT:PSS lags behind the rapid development of organic solar cells due to its low conductivity, acidity, and poor electron‐blocking capabilities. Herein, an innovative strategy is proposed to regulate the intrinsic properties of PEDOT:PSS by incorporating molybdenum‐containing semiconductors (MoO3, MoS2), which is validated using the state‐of‐the‐art active layer consisting of PM6:Y6 in conventional devices. The addition of molybdenum‐containing semiconductors alters the aggregation morphology of the PEDOT:PSS layer, increasing its conductivity and reducing its acidity. Furthermore, the hole extraction and electron‐blocking ability are improved by changing the work function of the anode with the influence of the deep energy level and by forming a trap energy level to capture electrons. Consequently, when the interlayer is employed, a champion power conversion efficiency of 17.1% in the PM6:Y6 devices and 18.9% in organic solar cells composed of PM6:L8‐BO is achieved. The results, which enhance the intrinsic properties of PEDOT:PSS with molybdenum‐containing semiconductors, offer valuable guidelines for engineering anode interlayers to fabricate highly efficient non‐fullerene organic solar cells. [ABSTRACT FROM AUTHOR]

The cathode interlayer plays a vital role in organic solar cells, which can modify the work function of electrodes, lower the electron extraction barriers, smooth the surface of the active layer, and remove solvent residuals. However, the development of organic cathode interlayer lags behind the rapidly improved organic solar cells because their intrinsic high surface tension can lead to poor contact with the active layers. Herein, a double‐dipole strategy is proposed to enhance the properties of organic cathode interlayers, which is induced by incorporating nitrogen‐ and bromine‐containing interlayer materials. To verify this approach, the state‐of‐the‐art active layer composed of PM6:Y6 and two prototypical cathode interlayer materials, PDIN and PFN‐Br is selected. Using the cathode interlayer PDIN: PFN‐Br (0.9:0.1, in wt.%) in the devices can reduce the electrode work function, suppress the dark current leakage, and improve charge extractions, leading to enhanced short circuit current density and fill factor. The bromine ions tend to break from PFN‐Br and form a new chemical bond with the silver electrode, which can adsorb extra dipoles directed from the interlayer to silver. These findings on the double‐dipole strategy provide insights into the hybrid cathode interlayers for efficient non‐fullerene organic solar cells. [ABSTRACT FROM AUTHOR]

With the emergence of nonfullerene acceptors (NFAs), single junction organic solar cells (OSCs) have achieved power conversion efficiencies (PCEs) of over 19%. Due to the intrinsic efficiency limits in low-bandgap NFA OSCs, the donor–to–acceptor energy transfer and acceptor–to–donor hole transfer have considerable impacts on the performance of the OSCs. However, time-resolved ultrafast spectroscopy is often used to prove the energy transfer and hole transfer processes. Herein, we designed thin films and active layers with a tandem structure composed of donors/electron blocking layers/acceptors to demonstrate the occurrence of donor–to–acceptor fluorescence resonance energy transfer (FRET) and acceptor–to–donor hole transfer. By analyzing the steady state photoluminescence peak position and intensity with varied substrate temperatures, FRET from PTO2 to IDTT-IC or IDTT-4FIC and hole transfer from IDTT-IC or IDTT-4FIC to PTO2 were demonstrated. In addition, we monitored devices with a tandem structure active layer using short/long pass filters to excite the donor or acceptor selectively and further confirmed the occurrence of FRET and hole transfer during device operation. Our results proved the effect of FRET and hole transfer directly in thin films and devices, providing a feasible yet practical approach with easily accessible measurements other than ultrafast spectroscopy. [ABSTRACT FROM AUTHOR]

Active layer morphology is critical to determine the photovoltaic performance of organic solar cells (OSCs), and additive‐assisted morphology optimization is one of the most widely used strategies to fine tune the donor–acceptor network in the active layer. However, the postprocessing procedures and additive residues require additional efforts to maintain the device performance. Herein, a low‐cost, simple structural design and volatile solid additive 2,5‐diiodothiophene is demonstrated to effectively optimize the active layer morphology and prompt the photoelectric conversion efficiency (PCE) of OSCs without any post‐treatment, outperforming the devices fabricated with the prototypical volatile additive 1,4‐diiodobenzene. The 2,5‐diiodothiophene (DIT)‐optimized PM6:Y6 binary OSCs obtain a PCE of 17.48%, accompanied with reduced trap‐assisted charge recombination and balanced charge carrier mobility. In addition, we notice that the bromide and chlorine analogues of DIT can enhance the device performance to a certain extent as well. The findings suggest that the post‐treatment‐free nature of the thiophene‐based processing additives are promising candidates for tuning the active layer morphology, providing simple processability for large‐scale fabrication of OSCs. [ABSTRACT FROM AUTHOR]

Under artificial indoor light, the development of efficient photovoltaics has attracted massive attention due to the revolutionary growth involving the Internet of Things for riding low‐power wireless electronic gadgets. Among the variety of available photovoltaic technologies such as inorganics (i.e., silicon, copper indium gallium selenide, cadmium telluride), organic photovoltaics, and hybrid organic–inorganic perovskites photovoltaics (PPVCs), the PPVCs have been recognized as the most promising PVCs for indoor light energy harvesting applications. This suitability is related to various factors due to its significant absorption coefficient, tunable bandgap, remarkable defect tolerance, better optoelectronic properties, and straightforward fabrication process. However, several parameters interconnected to materials, processing conditions, architecture, and indoor characterizations need to be optimized to enhance indoor photovoltaic efficiency, stability, and eco‐friendly nature. This review summarizes the latest research trends on organic–inorganic perovskite material‐based indoor PVCs, including the impact of composition tuning, choice of many practical layers, and device structures on their performance. Various challenges are highlighted to address before these indoor PPVCs are available in the commercial market. [ABSTRACT FROM AUTHOR]

Organic photodiodes (OPDs) have emerged as a potential alternative for inorganic photodiodes in light-detection technology due to their unique properties such as lightweight, flexibility, and tunable absorption range. However, the stability of OPDs is one of the main issues preventing the commercialization of OPDs. Herein, we performed a detailed characterization study of OPDs composed of all-polymer and polymer donors/small molecular acceptors to evaluate the detectivity and stability of devices. The small molecule acceptor Y5-Br and its polymerized counterpart PY-IT were selected to minimize the energy and absorption differences and paired with PM6. We found that the Y5-Br based device exhibited a higher detectivity and a lower dark current density due to the lesser extent of the trap density, whereas the PY-IT based device demonstrated a faster response time and impressive thermal/electrical stability. In addition, the analysis of the photosensitive layer morphology reveals that the all-polymer films showed remarkable thermal tolerance. In contrast, the thermal treatment resulted in apparent polymer and small molecule aggregations in the polymer–small molecule counterpart, leading to large scale phase segregations. Our findings suggest that the all-polymer composition is an efficient strategy to improve the stability of OPDs and provide a useful guidance for the commercial application of OPDs in the future. [ABSTRACT FROM AUTHOR]