Solution-processed few-layer MoS 2 fl akes are exploited as an active buffer layer in hybrid lead-halide perovskite solar cells (PSCs). Glass/FTO/compact-TiO 2 /mesoporous-TiO 2 /CH 3 NH 3 PbI 3 /MoS 2 /Spiro-OMeTAD/Au solar cells are realized with the MoS 2 fl akes having a twofold function, acting both as a protective layer, by preventing the formation of shunt contacts between the perovskite and the Au electrode, and as a hole transport layer from the perovskite to the Spiro-OMeTAD. As prepared PSC demonstrates a power conversion effi ciency ( η ) of 13.3%, along with a higher lifetime stability over 550 h with respect to reference PSC without MoS 2 (Δ η / η = −7% vs. Δ η / η = −34%). Large-area PSCs (1.05 cm 2 active area) are also fabricated to demonstrate the scalability of this approach, achieving η of 11.5%. Our results pave the way toward the implementation of MoS 2 as a material able to boost the shelf life of large-area perovskite solar cells in view of their commercialization.

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Two-dimensional (2D) semiconductors hold promises for electronic and optoelectronic applications due to their outstanding electrical and optical properties. Despite a short research history, a wide range of ‘proof-of-concept’ devices based on 2D materials have been demonstrated, highlighting their impact in advanced technology. Here we review the unique properties 2D semiconducting materials and their applications in terms of electronic and optoelectronic devices. We summarize all the engineering issues in 2D devices, including material quality, dielectric, and contacts. We also discuss recent advances of 2D semiconductor devices in electronic and optoelectronic applications. This review would help to understand superior performance and multifunctions of 2D semiconductor devices and guide us toward new device applications of 2D semiconductors.

High-efficiency organic photocathodes, based on regioregular poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester (rr-P3HT:PCBM) bulk heterojunction sandwiched between chargeselective layers, are emerging as efficient and low-cost devices for solar hydrogen production by water splitting. Nevertheless, stability issues of the materials used as charge-selective layers are hampering the realization of long-lasting photoelectrodes, pointing out the need to investigate novel and stable materials. Here, we propose MoS2 nano-flakes, produced by Li-aided exfoliation of bulk counterpart, as efficient atomic-thick hole-selective layer for rr-P3HT:PCBM-based photocathodes.We carried out a p-type chemical doping to tune on-demand the MoS2 Fermi level in order to match the highest occupied molecular orbital level of the rr-P3HT, thus easing the hole collection at the electrode. The as-prepared p-doped MoS2-based photocathodes reached a photocurrent of 1.21 mA cm -2 at 0 V vs. RHE, a positive onset potential of 0.56 V vs. RHE and a power-saved figure of merit of 0.43%, showing a 6.1-fold increase with respect to pristine MoS2-based photocathodes, under simulated 1 Sun illumination. Operational activity of the photocathodes over time and under 1 Sun illumination revealed a progressive stabilization of the photocurrents at 0.49 mA cm -2 at 0 V vs. RHE.These results pave the way towards the exploitation of layered crystals as efficiency-boosters for scalable hybrid organic H2-evolving photoelectrochemical cells.