DJL

The field of solution-processed photovoltaic cells is currently in its second spring. The dye-sensitized solar cell is a widely studied and longstanding candidate for future energy generation. Recently, inorganic absorber-based devices have reached new record efficiencies, with the benefits of all-solid-state devices. In this rapidly changing environment, this review sheds light on recent developments in all-solid-state solar cells in terms of electrode architecture, alternative sensitizers, and hole-transporting materials. These concepts are of general applicability to many next-generation device platforms.

The field of solution-processed photovoltaic cells is currently in its second spring, with solid-state devices incorporating novel inorganic absorbers reaching record efficiencies. This review sheds light on recent developments in all-solid-state solar cells in terms of electrode architecture, alternative sensitizers, and hole-transporting materials: concepts applicable to many next-generation device platforms.

Two-dimensional graphene–CdS (G–CdS) semiconductor hybrid nanosheets were synthesized in situ by graphene oxide (GO) quantum wells and a metal–xanthate precursor through a one-step growth process. Incorporation of G–CdS nanosheets into a photoactive film consisting of poly[4,8-bis-(2-ethyl-hexyl-thiophene-5-yl)-benzo[1,2-b:4,5-b]dithiophene-2,6-diyl]-alt-[2-(2-ethyl-hexanoyl)-thieno[3,4-b]thiophen-4,6-diyl] (PBDTTT-C-T) and [6,6]-phenyl C₇₀ butyric acid methyl ester (PC₇₀BM) effectively decreases the exciton lifetime to accelerate exciton dissociation. More importantly, the decreasing energy levels of PBDTTT-C-T, PC₇₀BM, and G–CdS produces versatile heterojunction interfaces of PBDTTT-C-T:PC₇₀BM, PBDTTT-C-T:G–CdS, and PBDTTT-C-T:PC₇₀BM:G–CdS; this offers multi-charge-transfer channels for more efficient charge separation and transfer. The charge transfer in the blend film also depends on the G–CdS nanosheet loadings. In addition, G–CdS nanosheets improve light utilization and charge mobility in the photoactive layer. As a result, by incorporation of G–CdS nanosheets into the active layer, the power-conversion efficiency of inverted solar cells based on PBDTTT-C-T and PC₇₁BM is improved from 6.0 % for a reference device without G–CdS nanosheets to 7.5 % for the device with 1.5wt % G–CdS nanosheets, due to the dramatically enhanced short-circuit current. Combined with the advantageous mechanical properties of the PBDTTT-C-T:PC₇₀BM:G–CdS active layer, the novel CdS-cluster-decorated graphene hybrid nanomaterials provide a promising approach to improve the device performance.

Two-dimensional exciton dissociation centers were fabricated in situ. By incorporating these centers into active layers (see figure, ITO=indium tin oxide, GO=graphene oxide), exciton dissociation and separation was dramatically improved with remarkably enhanced collecting and transporting efficiency of photoinduced electrons and holes, and thus elevated device performance.

Surface-enhanced Raman scattering (SERS) has become a mature vibrational spectroscopic technique during the last decades and the number of applications in the chemical, material, and in particular life sciences is rapidly increasing. This Review explains the basic theory of SERS in a brief tutorial and—based on original results from recent research—summarizes fundamental aspects necessary for understanding SERS and provides examples for the preparation of plasmonic nanostructures for SERS. Chemical applications of SERS are the centerpiece of this Review. They cover a broad range of topics such as catalysis and spectroelectrochemistry, single-molecule detection, and (bio)analytical chemistry.

Expanding vibrational spectroscopy: Since its first observation in 1973, surface-enhanced Raman scattering (SERS) has developed into a mature vibrational spectroscopic technique. The number of applications in chemistry as well as the material and life sciences is increasing rapidly. This Review summarizes the key concepts behind SERS and provides an overview of current applications in chemistry.

Semiconducting nanosheets with microscale lateral size are attractive building blocks for the fabrication of electronic and optoelectronic devices. The phase-controlled chemical synthesis of semiconducting nanosheets is of particular interest, because their intriguing properties are not only related to their size and shape, but also phase-dependent. Herein, a facile method for the synthesis of phase-pure, microsized, two-dimensional (2D) CuSe nanosheets with an average thickness of approximately 5 nm is demonstrated. These hexagonal-phased CuSe nanosheets were transformed into cubic-phased Cu_2−xSe nanosheets with the same morphology simply by treatment with heat in the presence of Cu^I cations. The phase transformation, proposed to be a template-assisted process, can be extended to other systems, such as CuS and Cu_1.97S nanoplates. Our study offers a new method for the phase-controlled preparation of 2D nanomaterials, which are not readily accessible by conventional wet-chemical methods.

Not fazed by change: A facile solution-based strategy was used for the preparation of microsized CuSe nanosheets. As-prepared CuSe with a hexagonal phase was transformed into Cu_2−xSe with a cubic phase through simple treatment with heat without damaging the shape of the original 2D nanosheets (see picture). The two kinds of nanosheets show different optical properties and are both promising building blocks for the construction of various devices.