Yingzhi Jin

Two region-specific selenium-based non-fullerene acceptors flanking conjugated side chains are compared with their sulfur-based analogue. mPh4F-TS with selenium at the outer positions show the most rigid skeleton, red-shifted absorption and compact stacking. The PM6 : mPh4F-TS organic solar cells exhibit the lowest energetic disorders, the highest charge carrier mobility and the best photon response, affording a top-ranking efficiency of >18 %.

Abstract

Central π-core engineering of non-fullerene small molecule acceptors (NF-SMAs) is effective in boosting the performance of organic solar cells (OSCs). Especially, selenium (Se) functionalization of NF-SMAs is considered a promising strategy but the structure-performance relationship remains unclear. Here, we synthesize two isomeric alkylphenyl-substituted selenopheno[3,2-b]thiophene-based NF-SMAs named mPh4F-TS and mPh4F-ST with different substitution positions, and contrast them with the thieno[3,2-b]thiophene-based analogue, mPh4F-TT. When placing Se atoms at the outer positions of the π-core, mPh4F-TS shows the most red-shifted absorption and compact molecular stacking. The PM6 : mPh4F-TS devices exhibit excellent absorption, high charge carrier mobility, and reduced energy loss. Consequently, PM6 : mPh4F-TS achieves more balanced photovoltaic parameters and yields an efficiency of 18.05 %, which highlights that precisely manipulating selenium functionalization is a practicable way toward high-efficiency OSCs.

Combining a ternary strategy with green solvents for overcoming the lack of high-performance wide-band-gap acceptors and harmful solvents suitable for indoor applications is demonstrated. The tetrahydrofuran-processed opaque and semitransparent modules not only exhibit promising efficiencies of 21.98% and 14.77% but also possess excellent operational stability. These outcomes drove us to construct a self-powered temperature-humidity gauge and an organic light-emitting diode device, demonstrating and highlighting the special use of this two-in-one ternary device.

FAPbI3 perovskite, which is prone to phase transition, is currently the best material to further improve the efficiency of single-junction perovskite solar cells (PSCs). We achieved efficient and stable FAPbI3 perovskites by a one-step method without antisolvent using ionic liquids (ILs) to control the precursor solution at the molecular level in humid air. The resulting optimized solar cells achieved efficiencies close to 24% with long operational stability over 1,000 h.

An ultrathin and dense phenol (Ph) self-assembly layer is first employed to anchor on the surface of polyethylenimine (PEI) to passivate the undesirable chemical reaction between PEI and the nonfullerene acceptors for highly efficient and stable organic solar cells.

The popular nonfullerene acceptors readily react with the amine group-containing low-work-function interfacial layer (polyethylenimine [PEI] or polyethylenimine ethoxylated [PEIE]), leading a severe “S” shape in the current density–voltage (J–V) characteristics of the nonfullerene organic solar cells (OSCs). Herein, a novel strategy is proposed to passivate this detrimental interfacial chemical reaction. Phenol (Ph) is anchored on the surface of PEI to form a thin and dense self-assembly layer, which can avoid a direct contact between the PEI and active layer. Moreover, the formed PEI–Ph bilayer cathode interface layer (CIL) can still low the work function of the bottom electrode. As a result, significant enhancement of the device performance is obtained for the PEI–Ph CIL-based nonfullerene OSCs and the “S” shapes in the J–V characteristics are removed. After Ph anchoring on the surface of PEI, the power conversion efficiencies are increased from 2.46% to 11.97% for the PTB7-Th:IEICO-4F active layer system and from 6.09% to 16.34% for the PM6:Y6 system, respectively. More importantly, the PEI–Ph CIL-based device displays a superior long-term and illumination stability.

A new approach for reliable performance evaluation of integrated solar charging systems is presented. It is applied to a three-electrode photosupercapacitor produced by integration of a high-performance organic solar cell with a mesoporous nitrogen-doped carbon nanosphere-based supercapacitor in a single device. The analysis shows 2% cycle efficiency and an unprecedently high photoelectrochemical energy conversion efficiency of 17%.

The global trend toward automatization and miniaturization of smart devices has triggered the development of reliable off-grid power sources with low economic and environmental impact. Such autonomy can be provided when a photovoltaic cell is integrated with an electrochemical double-layer capacitor in one monolithic power pack. This work demonstrates a reliable and straightforward approach to monolithically integrate high-performance organic solar cells with mesoporous nitrogen-doped carbon nanosphere-based supercapacitors in a single device with a three-electrode configuration. To assess the efficiency of the device, a novel approach is presented that relies on the direct monitoring of both integrating parts during illuminated and dark phases and accounts for possible losses. The evaluation with the standard literature approach shows an outstanding performance of the integrated photosupercapacitor with a peak photoelectrochemical energy conversion efficiency of 17%. However, this type of efficiency does not properly represent the real overall efficiency of the device. Based on the newly developed efficiency calculation, a more modest overall cycle efficiency of 2% is obtained, which represents the overall performance of the integrated device in a better way. This versatile evaluation approach is applicable for all kinds of integrated multifunctional photoconversion–storage systems.

While ternary solar cells regularly outperform their binary counterparts, their device physics are poorly understood, hampering rational design. Herein, numerical modeling is compared to the literature and own experimental data to assess the merits of various conceptual models that have previously been proposed. It is found that only the cascade model provides a consistent picture.

Mixing a third compound into the active layer of an organic bulk heterojunction solar cell to form a ternary system has become an established way to improve performance. Various models, based on different assumptions regarding the active layer morphology and the energetics, have been proposed but there is neither consensus on the applicability of the various assumptions to different experimental systems, nor on the actual device physics of these, mostly qualitative, models. Kinetic Monte Carlo simulations are used to investigate the role of morphology and relative energy levels of the constituent materials. By comparing with experimental current–voltage characteristics, a consistent picture arises when the (minority) third compound is predominantly incorporated between the other (majority) compounds and has energy levels that are intermediate to those of the binary host. Even if morphologically imperfect, the resulting energy cascade promotes charge separation and reduces recombination, leading to higher fill factors and short-circuit current densities. The open-circuit voltage sits between that of the binary extremes, in agreement with data from an extensive literature review. This leads to selection criteria for third compounds in terms of energetics and miscibility that promote the formation of a cascade morphology in real and energy space.

Quaternary Organic Solar Cells

The design highlights the quaternary layer-by-layer strategy for OSCs. The middle part shows the blend acceptor layer and donor layer, forming a desirable vertical phase separation and continuous charge transport channel. Each color line represents a material. The magnifiers show the material skeleton structures. The bulb is lighted up when light shines on the device surface. This is shown by Jinyuan Zhang, Beibei Qiu, Juan Qiao, Yongfang Li, and co-workers in article number 2200496.

Two novel nonconjugated small-molecule zwitterions, 4-(1-methyl piperidin-1-ium-1-yl)butane-1-sulfonate (MPBS) and 3-(1-methylpiperidin-1-ium-1-yl)-propane-1-sulfonate (MPPS), are synthesized as the morphology control additives for the cathode interlayers of nonfullerene organic solar cells. Both these zwitterions are able to form intense interaction with amino terminal-substituted perylene diimide (PDIN). It improves the morphology of the cathode interlayer and helps the formation of the electron transfer network, which significantly improve the photovoltaic performance.

The cathode interlayer (CIL) has significant impact on the performance of organic solar cells (OSCs), including the abilities to align energy levels, form ohmic contacts between the active layer and the electrode, and promote the electron extraction and transportation. However, the developments of CILs are still far behind the rapid explosion of active layer materials, especially for these nonfullerene acceptors (NFAs). This research provides a brand-new CIL optimization approach by applying the nonconjugated small-molecule zwitterion (NSMZ) as the morphology control additives (MCAs). Two novel NSMZs, 4-(1-methyl piperidin-1-ium-1-yl)butane-1-sulfonate (MPBS) and 3-(1-methylpiperidin-1-ium-1-yl)-propane-1-sulfonate, are developed as MCAs for the improvements of short-circuit current, fill factor, and power conversion efficiency (PCE) in various solar cell systems of the classic active layers and CILs. The interaction mechanism is systematically investigated. With the reduced energy barrier and suppressed electron recombination, a champion PCE of 18.65% on binary NFA–OSCs is achieved by incorporating the zwitterion of MPBS into the cathode interlayer as the additive, which is among the highest efficiency of the reported binary OSCs. The application of the zwitterion as MCAs for the cathode interlayer opens a novel avenue for highly efficient OSCs.

Herein, two wide-bandgap A₂-A₁-D-A₁-A₂-type nonfullerene acceptors with different central cores, namely BTA501 and BTA502, are developed to improve the photovoltaic performance of high-voltage organic solar cells. Consequently, the device of J52-F: BTA501 achieves an open circuit voltage (V _OC) of 1.037 V with a PCE of 11.82%, which are among the highest values for high-voltage devices with V _OC above 1.0 V.

In recent years, the organic solar cells (OSCs) research hotspot is the modification of end groups and alkyl side chains of A-DA’D-A-type nonfullerene acceptors (NFAs). However, the development of novel NFAs by changing the different bridged atom substitution of the central core is lagging behind. Herein, two wide-bandgap A₂-A₁-D-A₁-A₂-type NFAs with different central cores, namely BTA501 and BTA502, are developed to improve the photovoltaic performance of high-voltage OSCs. BTA501 adopted an indacenodithiophene (IDT) core, whereas BTA502 applied a silaindacenodithiophene (SiIDT) core. Expectedly, the SiIDT-based BTA502 exhibits a higher lowest unoccupied molecular orbital level and wider bandgap than BTA501, which thus enhances the open-circuit voltage (V _OC) but slightly decreases the short-circuit current density (J _SC) of OSCs. Moreover, the stronger self-aggregation characteristics and weaker π–π stacking of BTA502 severely affect the exciton dissociation and charge transport. When blended with two classic p-type polymers J52-F and PTB7-Th, both combinations based on BTA502 exhibit inferior device performance compared with BTA501. Excitingly, the device of J52-F: BTA501 achieves a V _OC of 1.037 V with a power conversion efficiency of 11.82% and a J _SC of 15.89 mA cm⁻², which are among the highest values for high-voltage OSCs with V _OC above 1.0 V.

Slot-Die Coated Organic Solar Cell Devices and Modules using a Perylene Diimide Top Interlayer.

Cathode interlayers (CILs) in organic photovoltaics (OPVs) are actively being researched as they are critical for device stability and performance. Herein, N-annulated perylene diimide with a 2-ethyl-hexyl side chain (PDIN-EH) is demonstrated, which is facile to synthesize as compared with conventional CILs such as PFN-Br, exhibits solubility, and subsequent processability from ethanol. The PDIN-EH is evaluated as a CIL in an air-processed, slot-die coated OPV consisting of PEDOT:PSS as the hole transport layer, PM6:Y6C12 as the bulk heterojunction, and top silver cathode electrode. All the organic layers are slot-die coated from green solvents and devices achieve a power convention efficiency of more than 12%, a result that is among the best reported under ambient conditions for printed OPVs. Microscopy images reveal that the PDIN-EH affords smooth film formation when slot-die coated on top of PM6:Y6C12 bulk heterojunction for an improved contact with the Ag electrode. Furthermore, the fabrication of large-area OPV modules on glass and flexible (polyethylene terephthalate) substrates is successfully demonstrated, with five cells connected in series achieving efficiency over 7% and open-circuit voltage over 3.5 V. Herein, useful guidelines for achieving fully printed organic electronic devices from green solvents at a potential industrial scale are provided.

A novel fluorinated conjugated polymer, PM7-F, is developed through a simple method to incorporate fluorine atoms into the π-bridge units. The PM7-F:ITIC-based polymer solar cells exhibit a remarkable power conversion efficiency of 13.46% with a open-circuit volatage of 0.94 V, a short-circuit current of 20.79 mA cm⁻², and an fill factor of 68.87%.

Herein, a novel fluorinated conjugated polymer, PM7-F, as the donor material for polymer solar cells (PSCs) is developed. In contrast to previously reported synthetic methods for 3-fluorothiophene, a crucial intermediate, 3-fluoro-2-iodothiophene, is utilized, to shorten the synthetic route and ensure lower synthetic costs via a simple approach. The effects of fluorine substituent on the π-bridge unit are systematically investigated. PM7-F displays great planarity and a nearly linear backbone via its strong intramolecular noncovalent conformation locks. Due to the strong noncovalent contacts of F–S, F–π, and F–Cl, as well as the large dipole moment of carbon–fluorine (C–F), the fluorinated polymer PM7-F possesses redshifted absorption, a much deeper highest occupied molecular orbital level (−5.65 eV), better crystallinity, enhanced nanoscale morphology, efficient charge transport properties, and reduced recombination behaviors than its nonfluorine counterpart. As a result, the PM7-F:ITIC-based PSCs exhibit a remarkable power conversion efficiency of 13.46% with a open-circuit voltage of 0.94 V, a short-circuit current of 20.79 mA cm⁻², and an fill factor of 68.87%. Herein, it is indicated that fluorination π-bridge provided a feasible approach to obtain low-cost and high-efficiency polymer donors.

The copolymerization strategy with a pentacyclic aromatic lactam acceptor unit integration is used to improve the device processability in nonhalogen solvents, resulting in semitransparent organic solar cells (ST-OSCs) with a maximum power conversion efficiency of 14.6%, an average visible transmittance of 22.5%, and a plant growth factor of 26%, making them one of the best-performing ST-OSCs for photovoltaic greenhouse applications.

Semitransparent organic solar cells (ST-OSCs) offer unique features such as spectral tunability and see-through function, giving them great potential in photovoltaic (PV) agriculture. However, the combination of sufficient average visible transmittance (AVT) and high power conversion efficiency (PCE) with eco-friendly device fabrication has always been a key issue. Herein, a simple but effective strategy by incorporating pentacyclic aromatic lactam acceptor unit (TPTI) in copolymer donors for toluene processed high-efficiency ST-OSCs is performed. The comparisons between D18- and DEH-X-based ST-OSCs demonstrate the effect of TPTI inserting on the polymer main skeleton can not only lower the energy level, improve the processability in nonhalogen solvent, tune the ideal morphology for efficient charge dissociation, but also control a photon transport window suitable for plant absorption. Therefore, the resulting OSCs processed with toluene exhibit a PCE of 14.6% with an AVT of 22%, which represents one of the highest values for ST-OSCs made from nonhalogenated solvents. What's more, it is found that plant growth under ST-OSCs filtered light is comparable with that under natural light. Herein, a guide for developing high-performance ST-OSCs is provided and the prospect of ST-OSCs for green manufacturing PV greenhouse application is demonstrated.

The conventional hole-extracting polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate in organic bulk-heterojunction (BHJ) photovoltaics is replaced with engineered self-assembled monolayers (SAMs). Combining the nanometre-thin SAM interlayers with an n-doped BHJ, organic photovoltaics with improved stability and a maximum power conversion efficiency of 18.9% are demonstrated.

Abstract

The influence of halogen substitutions (F, Cl, Br, and I) on the energy levels of the self-assembled hole-extracting molecule [2-(9H-Carbazol-9-yl)ethyl]phosphonic acid (2PACz), is investigated. It is found that the formation of self-assembled monolayers (SAMs) of [2-(3,6-Difluoro-9H-carbazol-9-yl)ethyl]phosphonic acid (F-2PACz), [2-(3,6-Dichloro-9H-carbazol-9-yl)ethyl]phosphonic acid (Cl-2PACz), [2-(3,6-Dibromo-9H-carbazol-9-yl)ethyl]phosphonic acid (Br-2PACz), and [2-(3,6-Diiodo-9H-carbazol-9-yl)ethyl]phosphonic acid (I-2PACz) directly on indium tin oxide (ITO) increases its work function from 4.73 eV to 5.68, 5.77, 5.82, and 5.73 eV, respectively. Combining these ITO/SAM electrodes with the ternary bulk-heterojunction (BHJ) system PM6:PM7-Si:BTP-eC9 yields organic photovoltaic (OPV) cells with power conversion efficiency (PCE) in the range of 17.7%–18.5%. OPVs featuring Cl-2PACz SAMs yield the highest PCE of 18.5%, compared to cells with F-2PACz (17.7%), Br-2PACz (18.0%), or I-2PACz (18.2%). Data analysis reveals that the enhanced performance of Cl-2PACz-based OPVs relates to the increased hole mobility, decreased interface resistance, reduced carrier recombination, and longer carrier lifetime. Furthermore, OPVs featuring Cl-2PACz show enhanced stability under continuous illumination compared to ITO/PEDOT:PSS-based cells. Remarkably, the introduction of the n-dopant benzyl viologen into the BHJ further boosted the PCE of the ITO/Cl-2PACz cells to a maximum value of 18.9%, a record-breaking value for SAM-based OPVs and on par with the best-performing OPVs reported to date.

Sodium-intercalated manganese oxides (NMO _x ) with intercalating sodium ions and water crystals are fabricated for aqueous asymmetric supercapacitors (ASCs). Systematical characterizations verify that the charge storage mechanism of NMO _x is governed by hydrated cation intercalation and deintercalation. The assembled ASC displays a landmark energy density of 88.9 W h kg⁻¹ and ultra-long cycle performance (92.7% retention after 50 000 cycles).

Abstract

Nanostructured birnessite with tunneled structures and nearly ideal capacitive behaviors are attractive as electrode material for aqueous asymmetric supercapacitors (ASCs). However, their practical application is hindered by inadequate structural stability, sluggish reaction kinetics, and the lack of deeper understanding of electrochemical mechanisms. Herein, oxygen defect modulated sodium-intercalated manganese oxides (Na_0.55Mn₂O_4-x ·1.5H₂O, abbreviated as NMO_x) with intercalating sodium ions and water crystals are massively fabricated, which can enable fast diffusion of cations and good structural stability. Systematical in situ and ex situ characterizations verify that the preeminent capacitive charge storage of NMO_x is governed by interlayer cation intercalation and deintercalation, accompanied by interlayer spacing expansion/contraction. Subsequently, a horizontally oriented carbon nanotube microfilm with outstanding electrical conductivity and electrolyte wettability is reported for aqueous ASCs, which exhibits a wide operating voltage (2.4 V), a high energy density of 88.9 W h kg⁻¹, and a superb cycle performance (92.7% retention after 50 000 cycles). Furthermore, a flexible planar ASC is prepared with landmark volumetric energy/power densities (60.2 mW h cm⁻³, 23.7 W cm⁻³), and excellent mechanical flexibility. This study provides not only an effective approach to fabricate tailoring structure and remarkable electrochemical properties of birnessite material, but also a deeper understanding of the charge storage mechanisms.

The interfacial engineering using hole-selective self-assembled monolayers is vital to enhance power conversion efficiencies and stabilities of next generation photovoltaics.

Abstract

Inverted type perovskite solar cells (PSCs) have recently emerged as a major focus in academic and industrial photovoltaic research. Their multiple advantages over conventional PSCs include easy processing, hysteresis-free behavior, high stability, and compatibility for tandem applications. However, the maximum power conversion efficiency (PCE) of inverted PSCs still lags behind those of conventional PSCs because suitable charge-selective materials for inverted PSCs are limited. In this study, excellent hole-selective materials for inverted PSCs are introduced. A series of tricyclic aromatic rings containing O, S, or Se, respectively, as a core heteroatom, along with a phosphonic acid anchor, form a self-assembled monolayer (SAM) that directly contacts the perovskite absorber. The influence of heteroatoms in the aromatic structure on the molecular energetics and operating characteristics of the corresponding inverted PSCs is investigated using complementary experimental techniques as well as density functional theory (DFT) calculations. It is found that all of the SAMs formed an energetically well-aligned interface with the perovskite absorber. The interaction energy between the Se-containing SAM and perovskite absorber is the strongest among the series and it reduces the interfacial defect density, in turn leading to an extended charge carrier lifetime. As a result, PSCs incorporating the Se-containing SAM achieves a PCE of 22.73% and retains ≈96% of their initial efficiency after a maximum power point tracking test of 500 h without encapsulation under ambient conditions. All of the SAMs are then employed in organic solar cells (OSCs). Again, the Se-containing SAM-based OSCs demonstrates the highest PCE of 17.9% among the three molecular SAM-based OSCs. This study demonstrates the great potential for precisely engineered SAMs for use in high-performance solar cells.

Organic Solar Cells

In article number 2204871, Dong-Yu Kim and co-workers propose water treatment by inducing vortex agitation in the stirring process of the active solution for organic solar cells, which can yield good dispersion of donors and acceptors. The introduced water content for the water treatment is universally optimized in small (0.1 cm²) and large (10 cm²) organic solar cells with improved final device efficiency and stability.

A dopant-free polymeric hole-transport material (HTM) PFBTI is successfully developed for PVSCs. The suitable energy levels, high hole mobility, and excellent surface passivation effects endow PFBTI-based organic/inorganic hybrid PVSCs with a promising PCE of 23.1% and much-enhanced stability. PFBTI can be further used in inorganic PVSCs and perovskite/organic tandem solar cells and achieve high PCEs.

Abstract

The development of hole-transport materials (HTMs) with high mobility, long-term stability, and comprehensive passivation is significant for simultaneously improving the efficiency and stability of perovskite solar cells (PVSCs). Herein, two donor–acceptor (D–A) conjugated polymers PBTI and PFBTI with alternating benzodithiophene (BDT) and bithiophene imide (BTI) units are successfully developed with desirable hole mobilities due to the good planarity and extended conjugation of molecular backbone. Both copolymers can be employed as HTMs with suitable energy levels and efficient defect passivation. Shortening the alkyl chain of the BTI unit and introducing fluorine atoms on the BDT moiety effectively enhances hole mobility and hydrophobicity of the HTMs, leading to improved efficiency and stability of PVSCs. As a result, the organic–inorganic hybrid PVSCs with PFBTI as the HTM deliver a power conversion efficiency (PCE) of 23.1% with enhanced long-term operational and ambient stability, which is one of the best efficiencies reported for PVSCs with dopant-free polymeric HTMs to date. Moreover, PFBTI can be applied in inorganic PVSCs and perovskite/organic tandem solar cells, achieving a high PCE of 17.4% and 22.2%, respectively. These results illustrate the great potential of PFBTI as an efficient and widely applicable HTM for cost-effective and stable PVSCs.

Nonfullerene organic solar cells based on quasi-homojunction (QHJ) with extremely low donor contents (≤10 wt.%) are fabricated. A complete picture of the operation mechanisms of high-efficiency QHJ devices is illustrated, which is distinct from classical bulk heterojunction (BHJ) ones.

Abstract

In contrast to classical bulk heterojunction (BHJ) in organic solar cells (OSCs), the quasi-homojunction (QHJ) with extremely low donor content (≤10 wt.%) is unusual and generally yields much lower device efficiency. Here, representative polymer donors and nonfullerene acceptors are selected to fabricate QHJ OSCs, and a complete picture for the operation mechanisms of high-efficiency QHJ devices is illustrated. PTB7-Th:Y6 QHJ devices at donor:acceptor (D:A) ratios of 1:8 or 1:20 can achieve 95% or 64% of the efficiency obtained from its BHJ counterpart at the optimal D:A ratio of 1:1.2, respectively, whereas QHJ devices with other donors or acceptors suffer from rapid roll-off of efficiency when the donors are diluted. Through device physics and photophysics analyses, it is observed that a large portion of free charges can be intrinsically generated in the neat Y6 domains rather than at the D/A interface. Y6 also serves as an ambipolar transport channel, so that hole transport as also mainly through Y6 phase. The key role of PTB7-Th is primarily to reduce charge recombination, likely assisted by enhancing quadrupolar fields within Y6 itself, rather than the previously thought principal roles of light absorption, exciton splitting, and hole transport.

A new morphology control approach is developed to fabricate high-performance organic solar cells by utilizing the synergistic effect of 1-chloronaphthalene (CN) and dithieno[3,2-b:2′,3′-d]thiophene (DTT) additives. This approach exhibits general application in various active layer systems to achieve well-developed morphology, enabling outstanding power-conversion efficiency over 18.8% and fill factor exceeding 80% for the device based on PTQ10:m-BTP-PhC6:PC₇₁BM.

Abstract

Controlling the self-assembling of organic semiconductors to form well-developed nanoscale phase separation in the bulk-heterojunction active layer is critical yet challenging for building high-performance organic solar cells (OSCs). Particularly, the similar anisotropic conjugated structures between nonfullerene acceptors and p-type organic semiconductor donors raise more complexity on manipulating their aggregation toward appropriate phase separation. Herein, a new approach to tune the morphology of photoactive layer is developed by utilizing the synergistic effect of dithieno[3,2-b:2′,3′-d]thiophene (DTT) and 1-chloronaphthalene (CN). The volatilizable solid additive DTT with high crystallinity can restrict the over self-assembling of nonfullerene acceptors during the film casting process, and then allowing the refining of phase separation and molecular packing with the simultaneous volatilization of DTT under thermal annealing. Consequently, the PTQ10:m-BTP-PhC6:PC₇₁BM-based ternary OSCs processed by the dual additives of CN and DTT record a notable power-conversion efficiency of 18.89%, with a remarkable FF of 80.6%.

A novel fullerene molecular template with a solubility enhancer arm (R1) and a π–π interaction inducer arm (R2) is deliberately proposed. This design effort delivers the highest power conversion efficiency over 20% of the device with corresponding fulleropyrrolidine electron transport material for the first time.

Abstract

[6,6]-phenyl-C₆₁-butyric acid methyl ester remains indispensable as the electron transport material (ETM) for perovskite solar cells (PSCs), but its synthesis involves complicated multisteps with low productivity. In contrast, the potential of synthesizing simpler fulleropyrrolidine derivatives has long been overlooked, and little has been understood regarding their structure-dependent effects on photovoltaic (PV) performance. Herein, seven novel fulleropyrrolidine derivatives (F1–F7) are deliberately designed, synthesized, and comprehensively characterized in both solution and thin-film states and subsequently investigated as ETMs for PSCs. Notably, the F4 delivers the highest power conversion efficiencies over 20% of devices, which surpass all reported fulleropyrrolidine ETMs due to its optimal photoelectric property. Moreover, the structure-dependent effects of the fullerenes on PV parameters are uncovered, including solubility, intermolecular interaction, packing structure, and charge-transfer ability, which can guide the future design of high-performance and stable fullerene ETMs for PSCs.

A power conversion efficiency of 12.91% and an average visible transmittance of 22.49% are achieved in semitransparent organic photovoltaics (OPVs) with D18:N3 (0.7:1.6, wt/wt) as active layers. This work demonstrates that the wide bandgap polymer donor with narrow photon harvesting in the visible light range has great potential in preparing efficient semitransparent OPVs.

Abstract

Wide bandgap polymer D18 with narrow photon harvesting in visible light range and small molecule N3 with near-infrared photon harvesting are adopted for building semitransparent organic photovoltaics (OPVs). To find out the optimal D18:N3 weight ratio for semitransparent OPVs, series of opaque OPVs are built with a varied D18:N3 weight ratio. The power conversion efficiency (PCE) and fill factor can be maintained over 16% and 77% in the D18:N3 (0.7:1.6, wt/wt) based opaque OPVs, respectively. The average visible transmittance (AVT) of the corresponding blend films can be achieved over 50%, demonstrating the great potential in fabricating efficient semitransparent OPVs. The semitransparent OPVs based on D18:N3 (0.7:1.6, wt/wt) are fabricated by using 1 nm Au/(10, 15, 20 nm) Ag as cathode. The thickness of Ag layers is varied to balance the optical properties and electrical properties of semitransparent top electrode. The semitransparent OPVs with 10 nm Ag achieve the highest light utilization efficiency of 2.90% with a PCE of 12.91% and an AVT of 22.49%, which should be among the best performance of reported semitransparent OPVs. This work demonstrates that the wide bandgap polymer donor with narrow photon harvesting in visible light range has great potential in preparing efficient semitransparent OPVs.

A bulky low-work function (low-WF, 4.1 eV) PEDOT:PSS-TBA is presented via ion exchange. Superior to other low-WF materials, the PEDOT:PSS-TBA is stable under oxygen plasma, heat, or isopropanol sonication. By combining the low-WF PEDOT:PSS-TBA and high-WF PEDOT:PSS as the cathode and anode, respectively, as a proof of concept, organic solar cells with a three-layered structure (PEDOT:PSS-TBA/PM6:IT-4F/PEDOT:PSS) are demonstrated.

Abstract

Cathode with low work-function (WF) is a vital unit in optoelectronic devices. Yet, the stable cathode is still a big challenge. Here, PEDOT:PSS-TBA is reported among series of PEDOT:PSS-M, where PEDOT:PSS denotes poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), M refers to monovalent cation and TBA is tetrabutylammonium specifically, as a stable cathode. The PEDOT:PSS-TBA is synthesized via ion exchange with WF of 4.1–4.2 eV and its conductivity can be improved to 300 S cm⁻¹ by the additive. Meanwhile, PEDOT:PSS-TBA is stable even under plasma, heat, or isopropanol sonication. Organic solar cells (OSCs) are fabricated with indium tin oxide (ITO)/PEDOT:PSS-TBA and highly conductive PEDOT:PSS-TBA (with additive, hc-PEDOT:PSS) electrodes respectively. The OSCs display superior stability than the reference with ITO/ZnO as the cathode. As a proof of concept, solution-processed OSCs are demonstrated with a three-layered structure (hc-PEDOT:PSS-TBA/active layer/PEDOT:PSS), which proves PEDOT:PSS-TBA as a promising cathode for printable optoelectronic with a simplified structure.