wangzhaowei

A growth-temperature-mediated two-step chemical vapor deposition strategy is designed to synthesize MoS₂/WS₂ and WS₂/MoS₂ stacks on Au foils. Predominantly A–A stacked MoS₂/WS₂ and A–B stacked WS₂/MoS₂ are selectively achieved and confirmed. Relative enhancements or reductions in photocatalytic activities of MoS₂/WS₂ or WS₂/MoS₂ are observed under illumination, because the type-II band alignment enables directional electron flow from electrode to active site.

Solution-processed organic solar cells with promising photovoltaic performance and extraordinary high thermal stability are achieved by employing novel fullerene-based acceptors in combination with two state-of-the-art polymer donors. The findings demonstrated in this work underline the necessity and importance of novel acceptor design rules for highly efficient organic solar cells with excellent device stability.

A robust and expedient gas quenching method is developed for the solution deposition of hybrid perovskite thin films. The method offers a reliable standard practice for the fabrication of a non-exhaustive variety of perovskites exhibiting excellent film morphology and commensurate high performance in both regular and inverted structured solar cell architectures.

The charge-carrier balance strategy by interface engineering is employed to optimize the charge-carrier transport in inverted planar heterojunction perovskite solar cells. N,N-Dimethylformamide-treated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and poly(methyl methacrylate)-modified PCBM are utilized as the hole and electron selective contacts, respectively, leading to a high power conversion efficiency of 18.72%.

Ion migration and accumulation in perovskite and interface have recently attracted considerable research interest because it is closely related to carrier extraction and hence to the performance of perovskite solar cells. Here using specific optical probe techniques and perovskite, the authors investigate the effect of light illumination (soaking) at the CH₃NH₃PbI₃/spiro-OMeTAD and CH₃NH₃PbI₃/Phenyl-C61-butyric-acid-methyl ester interfaces, focusing on the dynamics of mobile ions and photoexcited carriers. Time dependent photoluminescence (PL) intensity, electron–hole recombination and optical microscopy images are used to monitor the illumination effects at the interface as a function of light illumination time and intensity. Under continuous illumination, the PL intensity exhibits dynamic quenching in the timescale of seconds to minutes. The authors attribute this PL quenching to the accumulation of mobile ions at the interface during light soaking. Only negative ions cause such PL quenching and the rate at which PL intensity decreases depends on the illumination intensity. The authors found that the accumulated ions also impede the extraction of photogenerated holes from the perovskite layer into spiro-OMeTAD, which increases electron–hole recombination. This investigation provides novel insight into the ion migration mechanism by light soaking and therefore its impact on the operation of a perovskite solar cell.

Light soaking effect at the CH₃NH₃PbI₃/spiro-OMeTAD and CH₃NH₃PbI₃/PCBM interfaces is investigated using time dependent photoluminescence (PL) intensity, time-resolved PL, and optical microscopy images, focusing on the dynamics of mobile ions and photoexcited carriers. Negative ion accumulation is found to result in PL quenching at the interface of perovskite and spiro, which impedes the extraction of photogenerated holes.

A tandem organic light-emitting diode (OLED) is an organic optoelectronic device that has two or more electroluminescence (EL) units connected electrically in series with unique intermediate connectors within the device. Researchers have studied this new OLED architecture with growing interest and have found that the current efficiency of a tandem OLED containing N EL units (N > 1) should be N times that of a conventional OLED containing only a single EL unit. Therefore, this new architecture is potentially useful for constructing high-efficiency, high-luminance, and long-lifetime OLED displays and organic solid-state lighting sources. In a tandem OLED, the intermediate connector plays a crucial role in determining the effectiveness of the stacked EL units. The interfaces in the connector control the inner charge generation and charge injection into the adjacent EL units. Meanwhile, the transparency and the thickness of the connector affect the light output of the device. Therefore, the intermediate connector should be made to meet both the electrical and optical requirements for achieving optimal performance. Here, recent advances in the research of the tandem OLEDs is discussed, with the main focus on material selection and interface studies in the intermediate connectors, as well as the optical design of the tandem OLEDs.

Recent advances of tandem organic light-emitting diodes (OLEDs) including the material selection, interface engineering, and optical design of numerous intermediate connectors are reviewed. Their interfaces are crucial in determining the driving voltage, efficiencies, and lifetime. The optical transparency, microcavity, light out-coupling, and voltage drop across the intermediate connectors have to be carefully considered for high-performance tandem OLEDs.

o-Chlorobenzaldehyde (CBA) is a derivative of chlorobenzene (CB). The boiling point of CBA is 212 °C, much lower than 332 °C for 1,8-diiodooctane (DIO). With CBA as solvent additive in CB host solvent, CBA could be fast removed during spin-coating 100, 200, and 300 nm thick thieno[3,4-b]thiophene/benzodithiophene polymer (PTB7):[6,6]-phenyl C₇₁-butyric acid methyl ester (PC₇₁BM) active layers, achieving power conversion efficiencies of 9.11%, 8.24%, and 7.11%, respectively, much higher than 7.53%, 5.71%, and 4.93% for corresponding DIO control devices with vacuum drying.

The work functions for charge transport layers in perovskite solar cells affect device performance significantly. In this work, the regular poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is modified by adding a polymer electrolyte PSS-Na to improve its HTL function in perovskite solar cells. The modified PEDOT:PSS films (called m-PEDOT:PSS) possess higher work function than the regular one. Its energy level matches the valence band of perovskite very well, leading to enhanced V_oc and PCE (power conversion efficiency). When CH₃NH₃PbI₃ is used as the light absorber, the cell with PEDOT:PSS HTL gives a V_oc of 0.96 V and a PCE of 12.35%, while the cell with m-PEDOT:PSS layer gives a V_oc of 1.11 V and a PCE of 15.56%. Enhanced V_oc and PCE are also achieved when CH₃NH₃PbI₂Br or CH₃NH₃PbBr₃ is used as the light absorber. The m-PEDOT:PSS/CH₃NH₃PbBr₃/PC₆₁BM solar cells demonstrate an outstanding V_oc of 1.52 V.

A modified poly(3,4-ethylenedioxythiophene) (PEDOT) layer is developed and used as the HTL for perovskite solar cells, leading to enhanced performance. Using m-PEDOT:PSS (1:2) as the HTL and CH₃NH₃PbI₃ as the light absorber, a V_oc of 1.11 V and a power conversion efficiency of 15.56% are achieved. A V_oc of 1.52 V is obtained from CH₃NH₃PbBr₃ solar cells, which is the highest V_oc for perovskite/PCBM solar cells.

The coordination effects of additives during perovskite crystal growth are investigated, and a novel technique to fabricate high-quality perovskite thin films by introduction of weak coordination additives (e.g., acetonitrile) in the precursors is demonstrated.

Influence of light exposure on cesium lead halide nanostructures has been explored. A discovery of photon driven transformation (PDT) in 2D CsPbBr₃ nanoplatelets is reported, in which the quantum-confined few-monolayer nanoplatelets will convert to bulk phase under very low irradiation intensity (≈20 mW cm⁻²). Benefiting from the remarkable emission color change during PDT, the multicolor luminescence photopatterns and facile information photo-encoding are established.