Recent Progress of Organic Photovoltaics with Efficiency over 17%

The power conversion efficiency (PCE) of organic photovoltaics (OPVs) has exceeded 18% with narrow bandgap, non-fullerene materials Y6 or its derivatives when used as an electron acceptor. The PCE improvement of OPVs is due to strong photon harvesting in near-infrared light range and low energy loss. Meanwhile, ternary strategy is commonly recognized as a convenient and efficient means to improve the PCE of OPVs. In this review article, typical donor and acceptor materials in prepared efficient OPVs are summarized. From the device engineering perspective, the typical research work on ternary strategy and tandem structure is introduced for understanding the device design and materials selection for preparing efficient OPVs.

Monolithic Perovskite-Carrier Selective Contact Silicon Tandem Solar Cells Using Molybdenum Oxide as a Hole Selective Layer

Monolithic perovskite–silicon tandem solar cells with MoOx hole selective contact silicon bottom solar cells show a power conversion efficiency of 8%. A thin 15 nm-thick MoOx contact to n-type Si was used instead of a standard p+ emitter to collect holes and the SiOx/n+ poly-Si structure was deposited on the other side of the device for direct tunneling of electrons and this silicon bottom cell structure shows ~15% of power conversion efficiency. With this bottom carrier selective silicon cell, tin oxide, and subsequent perovskite structure were deposited to fabricate monolithic tandem solar cells. Monolithic tandem structure without ITO interlayer was also compared to confirm the role of MoOx in tandem cells and this tandem structure shows the power conversion efficiency of 3.3%. This research has confirmed that the MoOx layer simultaneously acts as a passivation layer and a hole collecting layer in this tandem structure.

Characterisation of the S1 satellite DNA family in Rana dalmatina

In this study, the DNA of Rana dalmatina was digested with Asp 718I and the two bands of highly repeated DNA produced were cloned and characterised. The largest fragment (494 bp) corresponded to the entire repetitive unit of the major satellite DNA (RdS1a), while the smaller fragment of 385 bp corresponded to the major fragment of RdS1a produced by digestion. A fragment of 332 bpbcorresponding to the repetitive unit of satellite S1b (RdS1b) was instead achieved by digestion with Eco RV. RdS1b is highly homologous to the corresponding portion of the repetition of RdS1a and presents the first 36 bp repeated and inverted. This suggested that RdS1b would have been derived from satellite S1a by two distinct and subsequent events. Further, the high sequence homology and length between RdS1a and the S1a of Rana italica (RiS1a) confirmed the hypothesis that the satellite S1a is antecedent to S1b and inherited from a common ancestor. Southern blots of R. dalmatina genomic DNA digested with Asp 718I produced hybrid bands of fragments of different sizes containing in addition to the satellite S1a, also one or more copies of the S1b satellites. The only sequenced band at the moment corresponded to the repetitive unit of the satellite RdS1a + b (826 bp) deleted of the fragment Asp 718I less than RdS1a (109 bp), while the other double bands should almost certainly correspond to repetitive units of satellites RdS1a + 2b and RdS1a + 3b. Our data suggested different satellite DNA organisation in R. dalmatina, including the tandem structure of the repetitive units of the RdS1a or RdS1b. Our data also suggested the existence in R. dalmatina of at least four different types of hybrid repeating units in all the populations examined.

All-Solid-State Proton-Based Tandem Structure Achieving Ultrafast Switching Electrochromic Windows

All-solid-state electrochromic devices (ECDs) for smart-window applications currently suffer from limited ion diffusion speed, which lead to slow coloration and bleaching processes. Here, we design an all-solid-state tandem structure with protons as diffusing species achieving an ultrafast switching ECD. We use WO3 as the electrochromic material, while poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) as the solid-state proton source to enable fast switching. This structure by itself exhibits low optical modulation (i.e., difference of on/off transmittance). We further introduce a solid polymeric electrolyte layer on top of PEDOT:PSS to form a tandem structure, which provides Na+ ions to PEDOT:PSS and pump protons there to the WO3 layer through ion exchange. Our new all-solid-state ECD features high optical modulation (>92% at 650 nm), fast response (coloration to 90% in 0.7 s and bleaching to 65% in 0.9 s and 90% in 7.1 s) and excellent stability (<10% degradation after 3000 cycles). Large-area (30×40 cm2) as well as flexible devices are fabricated to demonstrate the great potential for scaling up.

Scalable Production of Boron Quantum Dots for Broadband Ultrafast Nonlinear Optical Performance

A simple and effective approach based on the liquid phase exfoliation (LPE) method has been put forward for synthesizing boron quantum dots (BQDs). By adjusting the interactions between bulk boron and various solvents, the average diameter of produced BQDs is about 7 nm. The nonlinear absorption (NLA) responses of as-prepared BQDs have been systematically studied at 515 nm and 1030 nm. Experimental results prove that BQDs possess broadband saturable absorption (SA) and good third-order nonlinear optical susceptibility, which are comparable to graphene. The fast relaxation time and slow relaxation time of BQDs at 515 nm and 1030 nm are about 0.394–5.34 ps and 4.45–115 ps, respectively. The significant ultrafast nonlinear optical properties can be used in optical devices. Here, we successfully demonstrate all-optical diode application based on BQDs/ReS2 tandem structure. The findings are essential for understanding the nonlinear optical properties in BQDs and open a new pathway for their applications in optical devices.