以昇陳

The effect of Pd cross‐coupling catalyst traces on the physical processes in a non‐fullerene bulk‐heterojunction solar cell is investigated. The drop of the solar cell performance upon addition of systematically added amounts of tetrakis(triphenylphosphine)palladium(0) is explained by alteration of the morphology, charge carrier generation, recombination, and charge extraction.

Abstract

The effect of the cross‐coupling catalyst tetrakis(triphenylphosphine)palladium(0) (Pd(PPh₃)₄) on the performance of a model organic bulk‐heterojunction solar cell composed of a blend of poly([2,6′‐4,8‐di(5‐ethylhexylthienyl)benzo[1,2‐b;3,3‐b]dithiophene]{3‐fluoro‐2[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl}) (PTB7‐Th) donor and 3,9‐bis(2‐methylene‐((3‐(1,1‐dicyanomethylene)‐6,7‐difluoro)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene (IOTIC‐4F) non‐fullerene acceptor is investigated. The effect of intentional addition of different amounts of Pd(PPh₃)₄ on morphology, free charge carrier generation, non‐geminate bulk trap‐ and surface trap‐assisted recombination as well as bimolecular recombination and charge extraction is quantified. This work shows that free charge carrier generation is affected significantly, while the impact of Pd(PPh₃)₄ on non‐geminate recombination processes is limited because the catalyst does not facilitate efficient trap‐assisted recombination. The studied system shows substantial robustness towards the addition of Pd(PPh₃)₄ in small amounts.

Hybrid materials made of the P3HT conducting polymer and a copper(II) based molecular quantum bit are prepared. Mobile charge carriers are observed down to 15 K and quantum coherence up to 30 K. Hence, quantum coherence is preserved in the presence of mobile charge carriers paving the way to using these materials for molecular spintronics devices.

Abstract

Hybrid materials consisting of organic semiconductors and molecular quantum bits promise to provide a novel platform for quantum spintronic applications. However, investigations of such materials, elucidating both the electrical and quantum dynamical properties of the same material have never been reported. Here the preparation of hybrid materials consisting of conducting polymers and molecular quantum bits is reported. Organic field‐effect transistor measurements demonstrate that the favorable electrical properties are preserved in the presence of the qubits. Chemical doping introduces charge carriers into the material, and variable‐temperature charge transport measurements reveal the existence of mobile charge carriers at temperatures as low as 15 K. Importantly, quantum coherence of the qubit is shown to be preserved up to temperatures of at least 30 K, that is, in the presence of mobile charge carriers. These results pave the way for employing such hybrid materials in novel molecular quantum spintronic architectures.

In this work, an inexpensive and highly penetrating near‐infrared (NIR) light source combined with new organic NIR dyes allows the development of an unprecedented approach for bonding/debonding, reprocessing, reshaping, recycling, and self‐healing.

Abstract

Photoinduced thermal polymerization upon Near‐InfraRed (NIR) light has been recently reported in the literature as an efficient tool for polymer synthesis. In this work, a completely different approach is developed since polymeric materials containing a very low amount of a stimuli‐responsive compound are prepared by using a benchmark UV photoinitiator. As the stimuli‐responsive compound, an organic dye strongly absorbing in the near‐infrared region is selected. The heat released by its irradiation with an inexpensive and highly penetrating NIR light source allows the development of an unprecedented approach for reprocessing, reshaping, recycling, and self‐healing. Several parameters have been studied in order to determine their influence on the polymer temperature: the wavelength of the NIR irradiation, the irradiance of the NIR light source, the choice of heater (IR‐813 p‐toluenesulfonate or a squaraine dye), and the heater concentration. The thermoplastics bonding and debonding has also been studied and showed promising results since two pieces of polymers could be pasted together after a short time of NIR irradiation. Finally, self‐healing ability of the thermoplastic is investigated and furnished impressive results even for large scratches.

A layer‐by‐layer (LbL) deposition technique is used to successfully fabricate the high‐performance all‐polymer solar cells by synergistically controlling additive dosages in donor and acceptor solutions.

Abstract

In this work, an efficiency of 15.17% in the PBDB‐T/PYT all‐PSCs fabricated by a layer‐by‐layer (LbL) deposition technique is achieved by synergistically controlling additive dosages, which is not only higher than that (14.06%) of the corresponding bulk heterojunction (BHJ) device, but also the top efficient for all‐PSCs. Through the studies of physical dynamics and morphological characteristics, it is found that the LbL film can effectively improve optical and electronic properties, ensure exciton separation, charge generation and extraction, reduce trap‐assisted recombination, and facilitate hole transfer in LbL blends, thus achieving higher performance compared to its BHJ counterpart. Notably, the synergistic regulation of additive dosages in donor and acceptor solutions is also confirmed in the other three photovoltaic systems. Of particular note is that over 15% device performance is also achieved in the PBDB‐T/PYT LbL all‐PSCs fabricated via a blade‐coating technique, further demonstrating the great significance of this synergistic additive‐doping strategy for the printing fabrication of organic photovoltaics.

High performance perovskite solar modules (PSMs) are fabricated by introducing NH₄Cl to induce the formation of the intermediate phases. The PSMs show long‐term operational stability with a T ₈₀ lifetime under continuous light illumination exceeding 1600 h for a 5 × 5 cm² solar module and 1100 h for a 10 × 10 cm² solar module.

Abstract

In addition to high efficiencies, upscaling and long‐term operational stability are key pre‐requisites for moving perovskite solar cells toward commercial applications. In this work, a strategy to fabricate large‐area uniform and dense perovskite films with a thickness over one‐micrometer via a two‐step coating process by introducing NH₄Cl as an additive in the PbI₂ precursor solution is developed. Incorporation of NH₄Cl induces the formation of the intermediate phases of x[NH₄ ⁺]·[PbI₂Cl _x ] ^{x −} and HPbI_{3− x} Cl _x , which can effectively retard the crystallization rate of perovskite leading to uniform and compact full‐coverage perovskite layers across large areas with high crystallinity, large grain sizes, and small surface roughness. The 5 × 5 and 10 × 10 cm² perovskite solar modules (PSMs) based on this method achieve a power conversion efficiency (PCE) of 14.55% and 10.25%, respectively. These PSMs also exhibit good operational stability with a T ₈₀ lifetime (the time during which the solar module PCE drops to 80% of its initial value) under continuous light illumination exceeding 1600 h (5 × 5 cm²) and 1100 h (10 × 10 cm²), respectively.

Conformation effects of Y6‐type acceptors are systematically studied based on asymmetric design strategies. Z‐shape and W‐shape conformations‐based acceptors can help reduce energy loss in devices through significantly suppressed nonradiative energy loss. Benefiting from the high open‐circuit voltage of BP5T‐4F in the devices, ternary organic solar cells based on PM6:BP5T‐4F:CH1007 achieve a 17.2% efficiency.

Abstract

Y6, as a state‐of‐the‐art nonfullerene acceptor (NFA), is extensively optimized by modifying its side chains and terminal groups. However, the conformation effects on molecular properties and photovoltaic performance of Y6 and its derivatives have not yet been systematically studied. Herein, three Y6 analogs, namely, BP4T‐4F, BP5T‐4F, and ABP4T‐4F, are designed and synthesized. Owing to the asymmetric molecular design strategies, three representative molecular conformations for Y6‐type NFAs are obtained through regulating the lateral thiophene orientation of the fused core. It is found that conformation adjustment imposes comprehensive effects on the molecular properties in neat and blend films of these NFAs. As a result, organic solar cells (OSCs) fabricated with PM6:BP4T‐4F, PM6:BP5T‐4F, and PM6:ABP4T‐4F show high power conversion efficiency of 17.1%, 16.7%, and 15.2%, respectively. Interestingly, these NFAs with different conformations also show reduced energy loss (E _loss) in devices via gradually suppressed nonradiative E _loss. Moreover, by employing a selenium‐containing analog, CH1007, as the complementary third component, ternary OSCs based on PM6:BP5T‐4F:CH1007 (1:1.02:0.18) achieve a 17.2% efficiency. This work helps shed light on engineering the molecular conformation of NFAs to achieve high efficiency OSCs with reduced voltage loss.

In typical semitransparent organic photovoltaics (ST‐OPVs) that incorporate bulk heterojunction (BHJ) active layers, a compromise is made between the visible light transmittance (VLT) and power conversion efficiency (PCE). A new strategy with a sequential‐deposition (SD) active layer involving pseudo p–i–n structures provides ST‐OPVs with simultaneously higher PCE and VLT than that of the BHJ devices at the same layer thickness.

Abstract

Semitransparent organic photovoltaics (ST‐OPVs) have great potential for use in renewable energy technologies. In bulk‐heterojunction (BHJ) ST‐OPVs, a compromise is necessary between the visible light transmittance (VLT) and the power conversion efficiency (PCE). A sequential deposition (SD) strategy that involves individually depositing a polymer donor layer (D) and a small‐molecule acceptor layer (A) as the active layer is presented; where molecular diffusion occurring at the interfacial region results in a pseudo p–i–n structure. PBDB‐T‐2F(D)/Y6(A) ST‐OPVs are fabricated with different active layer thicknesses—at 115 nm, the SD (D:A/75:40 nm) and BHJ devices (D:A/1:1.2 w) provide the champion PCE of 12.91% (VLT of 14.5%) and 12.77% (VLT of 13.4%), respectively; at 85 nm, the SD (D:A/45:40 nm) and BHJ devices (D:A/1:1.2 w) provide a PCE of 12.22% (VLT of 22.2%) and 11.23% (VLT of 16.6%), respectively. This trend indicates SD devices have larger PCE and VLT values than the BHJ devices at a given active layer thickness, and the enhancements of PCE and VLT values by the SD structures against the BHJ structures become more pronounced as the active layer thickness reduced. The SD strategy provides a new approach for achieving ST‐OPVs with both high efficiency and high transparency.

A new class of polymer acceptors (P _As, P(BDT2BOY5‐X)) consisting of benzodithiophene (BDT) and non‐fullerene small molecule‐accepting units is developed, which shows excellent material compatibility with an efficient BDT‐based polymer donor (P _D). The resulting all‐polymer solar cells show excellent photovoltaic efficiency, thermal stability, and mechanical robustness at the same time, benefitting from the high chemical and molecular compatibilities between P _D and P _A.

Abstract

All‐polymer solar cells (all‐PSCs) are a highly attractive class of photovoltaics for wearable and portable electronics due to their excellent morphological and mechanical stabilities. Recently, new types of polymer acceptors (P _As) consisting of non‐fullerene small molecule acceptors (NFSMAs) with strong light absorption have been proposed to enhance the power conversion efficiency (PCE) of all‐PSCs. However, polymerization of NFSMAs often reduces entropy of mixing in PSC blends and prevents the formation of intermixed blend domains required for efficient charge generation and morphological stability. One approach to increase compatibility in these systems is to design P _As that contain the same building blocks as their polymer donor (P _D) counterparts. Here, a series of NFSMA‐based P _As [P(BDT2BOY5‐X), (X = H, F, Cl)] are reported, by copolymerizing NFSMA (Y5‐2BO) with benzodithiophene (BDT), a common donating unit in high‐performance P _Ds such as PBDB‐T. All‐PSC blends composed of PBDB‐T P _D and P(BDT2BOY5‐X) P _A show enhanced molecular compatibility, resulting in excellent morphological and electronic properties. Specifically, PBDB‐T:P(BDT2BOY5‐Cl) all‐PSC has a PCE of 11.12%, which is significantly higher than previous PBDB‐T:Y5‐2BO (7.02%) and PBDB‐T:P(NDI2OD‐T2) (6.00%) PSCs. Additionally, the increased compatibility of these all‐PSCs greatly improves their thermal stability and mechanical robustness. For example, the crack onset strain (COS) and toughness of the PBDB‐T:P(BDT2BOY5‐Cl) blend are 15.9% and 3.24 MJ m^–3, respectively, in comparison to the PBDB‐T:Y5‐2BO blends at 2.21% and 0.32 MJ m^–3.

Transparent luminescent solar concentrators (TLSC) incorporating massive‐downshifting phosphorescent nanoclusters and fluorescent organic molecules as ultraviolet and near‐infrared (NIR) selective‐harvesting luminophores, respectively, to maximize harvesting of the invisible solar spectrum are reported. The photoluminescence of both luminophores is tuned into the NIR to minimize visual impact. The dual‐band TLSCs show efficiencies over 3% with excellent visible transparency and color metrics.

Abstract

Visibly transparent luminescent solar concentrators (TLSC) can optimize both power production and visible transparency by selectively harvesting the invisible portion of the solar spectrum. Since the primary applications of TLSCs include building envelopes, greenhouses, automobiles, signage, and mobile electronics, maintaining aesthetics and functionalities is as important as achieving high power conversion efficiencies (PCEs) in practical deployment. In this work, massive‐downshifting phosphorescent nanoclusters and fluorescent organic molecules are combined into a TLSC system as ultraviolet (UV) and near‐infrared (NIR) selective‐harvesting luminophores, respectively, demonstrating UV and NIR dual‐band selective‐harvesting TLSCs with PCE over 3%, average visible transmittance (AVT) exceeding 75% and color metrics suitable for the window industry. With distinct wavelength‐selectivity and effective utilization of the invisible portion of the solar spectrum, this work reports the highest light utilization efficiency (PCE × AVT) of 2.6 for a TLSC system, the highest PCE of any transparent photovoltaic (TPV) devices with AVT greater than 70%, and outperforms the practical limit for non‐wavelength‐selective TPV.

The morphological and mechanical properties of a high‐efficiency ternary organic photovoltaic blend comprising fullerene and nonfullerene acceptors are characterized in detail. The device efficiency and crack‐onset strain are maximized at the same blend composition. Furthermore, the elastic modulus of ternary blends can be captured by a theoretical model. These relations pave the way to design efficient and stretchable organic photovoltaics.

Abstract

Ternary solar cells comprising both fullerene and nonfullerene acceptors have shown a rapid increase in power conversion efficiency, which holds promise in commercial applications. Despite the rapid progress, there is still a lack of fundamental understanding of the relations between microstructure and (photovoltaic/mechanical) properties in these ternary blend systems. In this work, the dependence of molecular packing, phase separation, mechanical properties, and photovoltaic performance on acceptor composition of a recently certificated ternary system is thoroughly investigated by combined scattering and microscopy characterizations. It is demonstrated that incorporating a small amount (20% by weight) PC₇₁BM to the PM6:N3 binary blend can afford the best device efficiency and the highest ductility simultaneously. This maximum performance is due to the optimized molecular order, orientational texture, and phase separation. Additionally, increasing the amount of PC₇₁BM results in higher elastic modulus, as probed by two distinct methods. A more crucial observation is that the elastic modulus of ternary blends can be well captured by an extended Halpin–Tsai model. This finding is expected to enable the prediction of the elastic modulus of various kinds of ternary blends that are widely used in solar cells and other electronics.

High‐performance organic semi‐transparent photovoltaic (ST‐OPV) devices are achieved by improving the light‐absorbing selectivity, that is, the light‐absorbing capability in invisible regions and light transmission in the visible region. Systematic optimization, including developing a numerical method for photo‐active layer screening, interface engineering, and optical manipulation, enables high‐performance ST‐OPVs with the best light utilization efficiency of 4.1%, ranking among the highest for ST‐OPVs.

Abstract

Semi‐transparent organic photovoltaics (ST‐OPVs) are promising solar windows for building integration. Improving the light‐absorbing selectivity, that is, transmitting the visible photons while absorbing the invisible ones, is a key step toward high‐performance ST‐OPV. To achieve this goal, the optical properties of the active layer, transparent electrode, and capping layer are comprehensively tailored, and a highly efficient ST‐OPV with good absorbing selectivity is demonstrated. First, a numerical method is established to quantify the absorbing selectivity of materials and devices, based on which, an infrared absorbing non‐fullerene acceptor, that is, H3, is selected among a large pool of photo‐active materials. Second, an ultra‐smooth transparent thin Ag layer with small granule size is developed via polyethylenimine wetting, which alleviates light scattering and improves the electric properties for ST‐OPV. Finally, as guided by optical simulation, a TeO₂ capping layer is deposited on top of the ultra‐thin Ag to further improve the light‐absorbing selectivity. As a result, the light utilization efficiency is significantly improved to 3.95 ± 0.02% (best ≈4.06%), with a good color rendering index of 76.85. These results make it one of the best among color‐neutral ST‐OPVs. This work stresses the importance of manipulating the light‐absorbing selectivity for high‐performance ST‐OPVs.

Nature Photonics, Published online: 25 January 2021; doi:10.1038/s41566-020-00749-9