Peng Wang

High efficiency dye-sensitized nanocrystalline solar cells based on ionic liquid polymer gel electrolyte

An ionic liquid polymer gel containing 1-methyl-3-propylimidazolium iodide (MPII) and poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) has been employed as quasi-solid-state electrolyte in dye-sensitized nanocrystalline TiO2 solar cells with an overall conversion efficiency of 5.3% at AM 1.5 illumination.

Ultrasensitive and Broadband MoS2 Photodetector Driven by Ferroelectrics

A few-layer MoS2 photodetector driven by poly(vinylidene fluoride-trifluoroethylene) ferroelectrics is achieved. The detectivity and responsitivity are up to 2.2 × 10(12) Jones and 2570 A W(-1), respectively, at 635 nm with ZERO gate bias. E(g) of MoS2 is tuned by the ultrahigh electrostatic field from the ferroelectric polarization. The photoresponse wavelengths of the photodetector are extended into the near-infrared (0.85-1.55 μm).

Stable ⩾8% efficient nanocrystalline dye-sensitized solar cell based on an electrolyte of low volatility

We demonstrate a ⩾8% efficient nanocrystalline dye-sensitized solar cell retaining over 98% of its initial performance after 1000 h of accelerated tests subjected to thermal stress at 80 °C in the dark. Device degradation was also negligible following 1000 h of visible light soaking at 60 °C. This high performance and stable device was realized by using a robust electrolyte of low volatility in conjunction with the amphiphilic ruthenium sensitizer [Ru(4,4′-dicarboxylic acid-2,2′-bipyridine)(4,4′-bis(p-hexyloxystyryl)-2,2′-bipyridine)(NCS)2], coded as K-19, which was grafted together with 1-decylphosphonic acid on the mesoporous titania film acting as photoanode.We demonstrate a ⩾8% efficient nanocrystalline dye-sensitized solar cell retaining over 98% of its initial performance after 1000 h of accelerated tests subjected to thermal stress at 80 °C in the dark. Device degradation was also negligible following 1000 h of visible light soaking at 60 °C. This high performance and stable device was realized by using a robust electrolyte of low volatility in conjunction with the amphiphilic ruthenium sensitizer [Ru(4,4′-dicarboxylic acid-2,2′-bipyridine)(4,4′-bis(p-hexyloxystyryl)-2,2′-bipyridine)(NCS)2], coded as K-19, which was grafted together with 1-decylphosphonic acid on the mesoporous titania film acting as photoanode.

Quasi-solid-state dye sensitized solar cells with 1,3:2,4-di-O-benzylidene-D-sorbitol derivatives as low molecular weight organic gelators

1,3:2,4-Di-O-benzylidene-D-sorbitol (DBS) and its derivatives are efficient gelators to solidify organic solvents over a wide range of polarity. In this paper we demonstrate the usefulness of certain DBS derivatives as efficient gelators to form thermoreversible gels in electrolyte solutions which are of particular interest for solar cell applications. The adjustable, high sol–gel phase transition temperature of 1,3:2,4-di-O-dimethylbenzylidene-D-sorbitol (DMDBS) with a 3-methoxypropionitrile-based electrolyte made this particular organic gelator very attractive in dye sensitized solar cells. For example, with an amphiphilic ruthenium dye and a quasi-solid-state gel electrolyte system based on 1,3:2,4-di-O-dimethylbenzylidene-D-sorbitol/3-methoxypropionitrile, a stable overall solar energy conversion efficiency of 6.1% was achieved at AM 1.5 sunlight illumination (99.8 mW cm−2).

Wafer-scale arrayed p-n junctions based on few-layer epitaxial GaTe

Two-dimensional (2D) materials have attracted substantial attention in electronic and optoelectronic applications with the superior advantages of being flexible, transparent, and highly tunable. Gapless graphene exhibits ultra-broadband and fast photoresponse while the 2D semiconducting MoS2 and GaTe exhibit high sensitivity and tunable responsivity to visible light. However, the device yield and repeatability call for further improvement to achieve large-scale uniformity. Here, we report a layer-by-layer growth of wafer-scale GaTe with a high hole mobility of 28.4 cm2/(V·s) by molecular beam epitaxy. The arrayed p-n junctions were developed by growing few-layer GaTe directly on three-inch Si wafers. The resultant diodes reveal good rectifying characteristics and a high photovoltaic external quantum efficiency up to 62% at 4.8 µW under zero bias. The photocurrent reaches saturation fast enough to capture a time constant of 22 µs and shows no sign of device degradation after 1.37 million cycles of operation. Most strikingly, such high performance has been achieved across the entire wafer, making the volume production of devices accessible. Finally, several photoimages were acquired by the GaTe/Si photodiodes with reasonable contrast and spatial resolution, demonstrating the potential of integrating the 2D materials with silicon technology for novel optoelectronic devices.