Perovskite/silicon tandem solar cells with bilayer interface passivation.

Two-terminal monolithic perovskite/silicon tandem solar cells demonstrate huge advantages in power conversion efficiency compared with their respective single-junction counterparts1,2. However, suppressing interfacial recombination at the wide-bandgap perovskite/electron transport layer interface, without compromising its superior charge transport performance, remains a substantial challenge for perovskite/silicon tandem cells3,4. By exploiting the nanoscale discretely distributed lithium fluoride ultrathin layer followed by an additional deposition of diammonium diiodide molecule, we have devised a bilayer-intertwined passivation strategy that combines efficient electron extraction with further suppression of non-radiative recombination. We constructed perovskite/silicon tandem devices on a double-textured Czochralski-based silicon heterojunction cell, which featured a mildly textured front surface and a heavily textured rear surface, leading to simultaneously enhanced photocurrent and uncompromised rear passivation. The resulting perovskite/silicon tandem achieved an independently certified stabilized power conversion efficiency of 33.89%, accompanied by an impressive fill factor of 83.0% and an open-circuit voltage of nearly 1.97 V. To the best of our knowledge, this represents the first reported certified efficiency of a two-junction tandem solar cell exceeding the single-junction Shockley-Queisser limit of 33.7%.

One-Stone-For-Three-Birds Strategy Using a Fullerene Modifier for Efficient and Stable Inverted Perovskite Solar Cells.

The electron extraction from perovskite/C60 interface plays a crucial role in influencing the photovoltaic performance of inverted perovskite solar cells (PSCs). Here, we develop a one-stone-for-three-birds strategy via employing a novel fullerene derivative bearing triple methyl acrylate groups (denoted as C60-TMA) as a multifunctional interfacial layer to optimize electron extraction at the perovskite/C60 interface. It is found that the C60-TMA not only passivates surface defects of perovskite via coordination interactions between C=O groups and Pb2+ cations but also bridge electron transfer between perovskite and C60. Moreover, it effectively induces the secondary grain growth of the perovskite film through strong bonding effect, and this phenomenon has never been observed in prior art reports on fullerene related studies. The combination of the above three upgrades enables improved perovskite film quality with increased grain size and enhanced crystallinity. With these advantages, C60-TMA treated PSC devices exhibit a much higher power conversion efficiency (PCE) of 24.89 % than the control devices (23.66 %). Besides, C60-TMA benefits improved thermal stability of PSC devices, retaining over 90 % of its initial efficiency after aging at 85 °C for 1200 h, primarily due to the reinforced interfacial interactions and improved perovskite film quality.

A recyclable dispersant based on carbomer utilizing controllable viscosity for high-efficiency dispersion of carbon fibers.

Good dispersion of carbon fibers is important for the carbon paper production, which is usually achieved using low carbon fiber concentrations and disposable dispersants. In this study, we developed carbomer as a recyclable and high-efficiency dispersant for carbon fibers. When the carbon fiber concentration was 0.1 wt%, carbon fiber suspension showed improved dispersion performance as increasing the carbomer dosage. It exhibited low Turbiscan Stability Index (TSI) of 0.41 and small change of delta backscattering between -0.5 to 0.8 % when using 0.5 wt% carbomer. However, the good dispersibility fade away when increasing the concentration of carbon fibers. Subsequently, the pH of the carbon fiber suspension was adjusted to 7.0 to improve the dispersibility by increasing the viscosity, but causing a worse flowability. Then the pH was further adjusted to 13.0 to ensure good flowability in the wet-forming process and good dispersibility at carbon fiber concentration of 0.5 wt%. More importantly, the dispersant was successfully recycled and still exhibited excellent dispersion effects for carbon fibers after 5 cycles. Notably, the high-efficiency dispersion of carbon fibers and the recyclability of dispersant were achieved simultaneously for the first time, which is suitable for the eco-friendly and sustainable production of carbon paper.

Family-wide Characterization of Methylated DNA Binding Ability of Arabidopsis MBDs.

13 MBD-containing genes (AtMBD1-13) have been identified in Arabidopsis thaliana so far, however, their DNA binding ability is still controversial. Here, we systematically measured the DNA binding affinities of these MBDs by ITC and EMSA binding assays, except for those of pseudogenes AtMBD3 and AtMBD13, and found that only AtMBD6 and AtMBD7 function as methylated DNA readers. We also found that the MBD of AtMBD5 exhibits very weak binding to methylated DNA compared to that of AtMBD6. To further investigate the structural basis of AtMBDs in binding to methylated DNA, we determined the complex structure of the AtMBD6 MBD with a 12mer mCG DNA and the apo structure of the AtMBD5 MBD. Structural analysis coupled with mutagenesis studies indicated that, in addition to the conserved arginine fingers contributing to the DNA binding specificity, the residues located in the loop1 and α1 are also essential for the methylated DNA binding of these MBDs in Arabidopsis thaliana, which explains why AtMBD5 MBD and the other AtMBDs display very weak or no binding to methylated DNA. Thus, our study here systematically demonstrates the DNA binding ability of the MBDs in Arabidopsis thaliana, which also provides a general guideline in understanding the DNA binding ability of the MBDs in other plants as a whole.

Boosting Antitumor Sonodynamic Therapy Efficacy of Black Phosphorus via Covalent Functionalization.

Sonodynamic therapy (SDT) triggered by ultrasound represents an emerging tumor therapy approach with minimally invasive treatment featuring nontoxicity and deep tissue-penetration, and its efficacy sensitively depends on the sonosensitizer which determines the generation of reactive oxygen species (ROS). Herein, for the first time covalently functionalized few-layer black phosphorus nanosheets (BPNSs) are applied as novel sonosensitizers in SDT, achieving not only boosted SDT efficacy but also inhibited cytotoxicity relative to the pristine BPNSs. Three different covalently functionalized-BPNSs are synthesized, including the first fullerene-functionalized BPNSs with C60 covalently bonded onto the surface of BPNSs (abbreviated as C60 -s-BP), surface-functionalized BPNSs by benzoic acid (abbreviated as BA-s-BP), and edge-functionalized BPNSs by C60 (abbreviated as C60 -e-BP), and the role of covalent functionalization pattern of BPNSs on its SDT efficacy is systematically investigated. Except C60 -e-BP, both surface-functionalized BPNSs (C60 -s-BP, BA-s-BP) exhibit higher SDT efficacies than the pristine BPNSs, while the highest SDT efficacy is achieved for BA-s-BP due to its strongest capability of generating the hydroxyl (·OH) radicals, which act as the dominant ROS to kill the tumor cells.

Fast Wetting of a Fullerene Capping Layer Improves the Efficiency and Scalability of Perovskite Solar Cells.

Fullerene derivatives, especially [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), have been widely applied as electron transport layers of inverted planar heterojunction perovskite solar cells (PSCs). However, the solution-processed PCBM capping layer suffers from limited surface wetting which hinders the improvement in efficiency and scalability of PSCs. Herein, we develop a facile hybrid solvent strategy that enables very fast wetting of the PCBM capping layer atop of the perovskite surface, leading to an improved interfacial contact and electron transport. The significantly enhanced wettability of the PCBM solution fulfilled through blending isopropyl alcohol into the commonly used chlorobenzene (CB) is attributed to the reduced surface tension while retaining viscosity. As a result, the electron mobility and electric conductivity of the PCBM capping layer increase by around two times, and the PSC devices exhibit the highest power conversion efficiency (PCE) of 19.92%, which is improved by ∼18% relative to that of the control device (16.78%). Importantly, this strategy is also applicable for other alcohols (ethanol and methanol) and CB blends. Moreover, the fast wetting approach enables us to deposit the PCBM capping layer using a facile drop-casting method, affording comparable PCEs to those obtained by the conventional spin-coating method, which is not achievable by using the conventional single solvent. This fast wetting PCBM capping layer also contributes to efficiency improvement of large-area (1 cm2) devices. These advances hold great potential for other scalable deposition methods such as blade-coating and slot-die coating.

Anchoring Fullerene onto Perovskite Film via Grafting Pyridine toward Enhanced Electron Transport in High-Efficiency Solar Cells.

Fullerene derivatives have been popularly applied as electron transport layers (ETLs) of inverted (p-i-n) planar heterojunction perovskite solar cells (iPSCs) due to their strong electron-accepting abilities, and so far, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) has been the most commonly used ETL, which suffers, however, from high cost due to the complicated synthetic route. Herein, novel pyridine-functionalized fullerene derivatives (abbreviated as C60-Py) were synthesized facilely via a one-step 1,3-dipolar cycloaddition reaction and applied as ETLs superior to PCBM in iPSC devices. Three pyridine-functionalized fullerene derivatives with different alkyl groups, including methyl, n-butyl, and n-hexyl, grafted onto the pyrrolidine moiety (abbreviated as C60-MPy, C60-BPy, and C60-HPy, respectively) were synthesized. According to cyclic voltammogram study, the chain length of the N-alkyl group has negligible influence on the molecular energy level of C60-Py. However, the ETL performance of C60-Py is sensitively dependent on the chain length of the N-alkyl group, with C60-BPy exhibiting the highest power conversion efficiency (PCE) of 16.83%, which surpasses that based on PCBM ETL (15.87%). The PCE enhancement of C60-BPy device is attributed to the coordination interactions between the pyridine moiety with the Pb2+ ion of CH3NH3PbI3 perovskite, which anchor C60-BPy onto perovskite film and reinforce the passivation of the trap state within the CH3NH3PbI3 perovskite film and suppress the nonradiative electron-hole recombinations, leading to enhanced electron transport reflected by the increase of short-circuit current density ( Jsc). The ambient stability of C60-HPy-based device is much better than that based on PCBM ETL since its long N-alkyl group can function as a superior encapsulating layer protecting the CH3NH3PbI3 layer from contact with the ambient moisture.