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The reported power conversion efficiencies (PCEs) of nonfullerene acceptor (NFA) based organic photovoltaics (OPVs) now exceed 14% and 17% for single‐junction and two‐terminal tandem cells, respectively. However, increasing the PCE further requires an improved understanding of the factors limiting the device efficiency. Here, the efficiency limits of single‐junction and two‐terminal tandem NFA‐based OPV cells are examined with the aid of a numerical device simulator that takes into account the optical properties of the active material(s), charge recombination effects, and the hole and electron mobilities in the active layer of the device. The simulations reveal that single‐junction NFA OPVs can potentially reach PCE values in excess of 18% with mobility values readily achievable in existing material systems. Furthermore, it is found that balanced electron and hole mobilities of >10−3 cm2 V−1 s−1 in combination with low nongeminate recombination rate constants of 10−12 cm3 s−1 could lead to PCE values in excess of 20% and 25% for single‐junction and two‐terminal tandem OPV cells, respectively. This analysis provides the first tangible description of the practical performance targets and useful design rules for single‐junction and tandem OPVs based on NFA materials, emphasizing the need for developing new material systems that combine these desired characteristics. The efficiency limits in non‐fullerene organic solar cells are examined using a numerical simulator. Power conversion efficiency (PCE) of over 18% using recently reported carrier mobility values and voltage losses, are predicted. Increasing the mobility to >10−3 cm2 V−1 s−1 and decreasing the recombination constant to <10−12 cm3 s−1 is shown to yield a single‐junction and 2T‐tandem cell with PCEs of >20% and >25%, respectively.

Photon interconversion in semiconductors is of fundamental importance for digital imaging and quantum sensing. Nonlinear processes such as triplet–triplet annihilation (TTA) offer photon upconversion (UC) at yields desired for solid‐state optoelectronic devices. Here, a multilayer molecular system where a near‐infrared (NIR) photosensitizer facilitates robust photon UC is presented. A molecular stack of 2,4‐Bis[4‐(N,N‐diisobutylamino)‐2,6‐dihydroxyphenyl] squaraine (DIB‐SQ): [6,6]‐Phenyl C61 butyric acid methyl ester (PCBM) is optimized for UC by fine‐tuning the PCBM loading to engineer charge transfer states (CT) to amplify triplet generation. This composite photosensitizer layer, at a 1:3 blend ratio in heterojunction with rubrene, drives triplet population density to levels desired for effective TTA. When paired with a fully optimized annihilator layer of tetraphenyldibenzoperiflanthene (DBP) doped rubrene, the sensitizer produces a photon upconversion quantum yield (ΦUC) of 1.36% at 690 nm, with a significantly low excitation intensity threshold for the onset of the linear regime of Ith = 60.5 mW cm−2. Time‐resolved photoluminescence, transient absorption spectroscopy, and magnetic field‐dependent photoluminescence measurements reveal a detailed balance of photoexcited states and formation of charge transfer states of triplet character (3CT), which work in tandem with molecular states to sensitize the triplet state (T1) of rubrene. This approach of harnessing near‐infrared photons presents a promising avenue for advancing solid‐state photon interconversion. A near‐infrared photosensitizer that facilitates efficient solid‐state photon upconversion by recycling triplets formed within a fullerene‐based donor–acceptor bulk‐heterojunction system is demonstrated. Spectroscopic investigations reveal that the energy of photogenerated charge transfer states of triplet character (3CT) is subsequently transferred to triplet states of rubrene, followed by triplet–triplet annihilation upconversion.

Charge manipulation is crucial in optoelectronic devices. The unoptimized interfacial charge injection/extraction in solution‐processed bulk‐heterojunction (BHJ) organic photodetectors (OPDs) presents significant challenges in achieving high detectivity and fast response speed. Here, we first develop an approach for intrinsic charge manipulation induced by molecularly engineered donors to block electron injection and facilitate hole extraction between the indium tin oxide (ITO) transparent anode and the photoactive layer. By utilizing a polymer donor with 3,4‐ethylenedioxythiophene (EDOT) as the conjugated side chain, a polymer‐rich layer forms spontaneously on the ITO substrate due to the increased oxygen interactions between ITO and EDOT. This results in electron‐blocking‐layer (EBL)‐free devices with lower dark current and noise without a reduction in responsivity compared to control devices. As a result, the EBL‐free devices exhibit a peak specific detectivity of 2.36 × 1013 Jones at 950 nm and achieve a −3 dB bandwidth of 30 MHz under −1 V. Enhanced stability is also observed compared to the devices with poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). This work demonstrates a new method to intrinsically manipulate charge injection in BHJ photoactive layers, enabling the fabrication of solution‐processed EBL‐free OPDs with high sensitivity, rapid response, and good stability. An intrinsic charge manipulation approach is first demonstrated for solution‐processed bulk‐heterojunction organic photodetectors (OPDs). Utilizing polymer donors with 3,4‐ethylenedioxythiophene side chains, a thin polymer‐rich layer is formed on the indium‐tin‐oxide anode to block electron injection and facilitate hole extraction. Thus, the OPDs exhibit high sensitivity and fast response without the need for electron‐blocking layers.

How to extend the photoresponse of perovskite solar cells (PVSCs) to the region of near‐infrared (NIR)/infrared light has become an appealing research subject in this field since it can better harness the solar irradiation. Herein, the typical fullerene electron‐transporting layer (ETL) of an inverted PVSC is systematically engineered to enhance device's NIR photoresponse. A low bandgap nonfullerene acceptor (NFA) is incorporated into the fullerene ETL aiming to intercept the NIR light passing through the device. However, despite forming type II charge transfer with fullerene, the blended NFA cannot enhance the device's NIR photoresponse, as limited by the poor dissociation of photoexciton induced by NIR light. Fortunately, it can be addressed by adding a p‐type polymer. The ternary bulk‐heterojunction (BHJ) ETL is demonstrated to effectively enhance the device's NIR photoresponse due to the better cascade‐energy‐level alignment and increased hole mobility. By further optimizing the morphology of such a BHJ ETL, the derived PVSC is finally demonstrated to possess a 40% external quantum efficiency at 800 nm with photoresponse extended to the NIR region (to 950 nm), contributing ≈9% of the overall photocurrent. This study unveils an effective and simple approach for enhancing the NIR photoresponse of inverted PVSCs. A low bandgap nonfullerene acceptor (NFA) is incorporated into fullerene electron‐transporting layer (ETL) of an inverted perovskite solar cell aiming to intercept the NIR light passing through the device. However, it cannot enhance the device's NIR photoresponse. Further adding a p‐type polymer effectively enhances the device's NIR photoresponse due to better cascade energy‐level alignment and increased hole mobility.

Three donor/acceptor (D/A)-type two-dimensional polythiophenes (PTs; PBTFA13, PBTFA12, PBTFA11) featuring difluorobenzothiadiazole (DFBT) derivatives as the conjugated (acceptor) units in the polymer backbone and tertbutyl-substituted triphenylamine (tTPA)-containing moieties as (donor) pendants have been synthesized and characterized. These PTs exhibited good thermal stabilities, broad absorption spectra, and narrow optical band gaps. The cutoff wavelength of the UV-Vis absorption band was red-shifted upon increasing the content of the DFBT units in the PTs. Bulk heterojunction solar cells having an active layer comprising blends of the PTs and fullerene derivatives [6,6] phenyl-C61/71-butyric acid methyl ester (PC61BM/PC71BM) were fabricated; their photovoltaic performance was strongly dependent on the content of the DFBT derivative in the PT. Incorporating a suitable content of the DFBT derivative in the polymer backbone enhanced the solar absorption ability and conjugation length of the PTs. The photovoltaic properties of the PBTFA13-based solar cells were superior to those of the PBTFA11- and PBTFA12-based solar cells.

The combination of lithium ion battery (LIB) and organic (polymer) solar cells is expected to deliver versatile self-rechargeable portable energy sources, but less attention has been paid to the charging characteristics of LIB-using polymer solar cells. Here we demonstrate that the LIB packs, which were prepared by using lithium cobalt oxide (LiCoO2) and graphite as a cathode and an anode, respectively, can be effectively charged by semi-solar modules of polymer:fullerene solar cells, of which bulk heterojunction (BHJ) layers are composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM). Results showed that the performance of semi-solar modules was not much degraded by connecting four single solar cells in series or in parallel, but their output power density was noticeably reduced by extending the number of single cells up to eight. The charging test disclosed that the output current density is of importance to speed up the LIB charging at the same output voltage.

Self-assembled donor–acceptor dyads are used as model nanostructured heterojunctions for local investigations by noncontact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM). With the aim to probe the photo-induced charge carrier generation, thin films deposited on transparent indium tin oxide substrates are investigated in dark conditions and upon illumination. The topographic and contact potential difference (CPD) images taken under dark conditions are analysed in view of the results of complementary transmission electron microscopy (TEM) experiments. After in situ annealing, it is shown that the dyads with longer donor blocks essentially lead to standing acceptor–donor lamellae, where the acceptor and donor groups are π-stacked in an edge-on configuration. The existence of strong CPD and surface photo-voltage (SPV) contrasts shows that structural variations occur within the bulk of the edge-on stacks. SPV images with a very high lateral resolution are achieved, which allows for the resolution of local photo-charging contrasts at the scale of single edge-on lamella. This work paves the way for local investigations of the optoelectronic properties of donor–acceptor supramolecular architectures down to the elementary building block level.

A bicontinuous network formed spontaneously upon film preparation is highly desirable for bulk-heterojunction (BHJ) organic solar cells (OSCs). Many donor-acceptor (D-A) type conjugated polymers can self-assemble into polymer fibrils in the solid state and such fibril-assembly can construct the morphological framework by forming a network structure, inducing the formation of ideal BHJ morphology. Our recent works have revealed that the fibril network strategy (FNS) can control the blend morphology in fullerene, non-fullerene and ternary OSCs. It has been shown that the formation of fibril network can optimize phase separation scale and ensure efficient exciton dissociation and charge carriers transport, thus leading to impressive power conversion efficiencies (PCEs) and high fill factor (FF) values. We believe that FNS will provide a promising approach for the optimization of active layer morphology and the improvement of photovoltaic performance, and further promote the commercialization of OSCs.

Photon Up‐Conversion In the Research Article (DOI: 10.1002/admi.202500897), Maciej Klein, Evan G. Moore, Ajay K. Pandey, and co‐workers describe a novel strategy for harnessing near‐infrared photons to advance solid‐state photon interconversion in molecular heterojunctions. The NIR‐absorbing molecular stack enables efficient triplet generation via charge‐transfer state formation, amplifying triplet population density and yielding high photon up‐conversion quantum efficiencies under incoherent, low‐intensity illumination. The underlying excitonic cascade makes it highly attractive for quantum sensing and photodetector technologies.

The introduction of the IDIC/ITIC families of non-fullerene acceptors has boosted the photovoltaic performances of bulk-heterojunction organic solar cells. The fine tuning of the photophysical, morphological and processability properties with the aim of reaching higher and higher photocurrent efficiencies has prompted uninterrupted worldwide research on these peculiar families of organic compounds. The main strategies for the modification of IDIC/ITIC compounds, described in several contributions published in the past few years, can be summarized and classified into core modification strategies and end-capping group modification strategies. In this review, we analyze the more recent advances in this field (last two years), and we focus our attention on the molecular design proposed to increase photovoltaic performance with the aim of rationalizing the general properties of these families of non-fullerene acceptors.