Ningyi Yuan

A promising alternative solvent of perovskite to induce rapid crystallization for high-efficiency photovoltaic devices

As solar cell structures based on planar heterojunctions have already demonstrated very impressive advances in cost-effectiveness and performance, many different solvents are being developed and gradually adopted for high-performance inorganic–organic hybrid perovskite solar cells. Here, we introduce a simple planar cell configuration with layers prepared in a fully solution-based process, in which dimethylacetamide (DMAC) serves as an effective precursor solvent that is comparable with N,N-dimethylformamide (DMF). The use of DMAC leads to a smooth and dense perovskite film via one-step deposition, whose ideal morphology enables solar cells to obtain a high power-conversion efficiency of 15.12%. We also studied the effect of different solvents through a computation of the stabilization energy between PbI2, CH3NH3I, and solvent molecules. These results offer insight into the promising directions for the development of solvent engineering.

Poly(ionic liquid)/ionic liquid/graphene oxide composite quasi solid-state electrolytes for dye sensitized solar cells

Poly(ionic liquid)/ionic liquid/graphene oxide (poly(IL)/IL/GO) composite gel electrolytes containing poly(1-butyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide), 1-propyl-3-methylimidazolium iodide and graphene oxide are prepared for dye-sensitized solar cells (DSSCs), without any volatile organic solvent. The conductivity of the composite electrolyte is significantly increased by adding an appropriate amount of GO, and the DSSCs based on composite electrolytes containing GO show higher power conversion efficiency performance and better long-term stability compared to those without GO. The DSSC based on the composite electrolytes which contain 2 wt% of GO show an overall power conversion efficiency of 4.83% under simulated AM 1.5 solar spectrum irradiation. The superior long-term stability of the DSSCs indicates that this type of composite electrolyte could overcome the drawbacks of volatile liquid electrolytes, and offer a feasible method to fabricate DSSCs in future practical applications.

A new oil/water interfacial assembly of sulphonated graphene into ultrathin films

A new oil/water interfacial assembling approach has been developed to fabricate ultrathin graphene films based on a combination of two established interfacial assembling techniques. This new approach integrates multiple advantages such as simple equipment requirements in traditional oil/water interfacial assembly and minimum demand on the feeding source in air/water interfacial assembly (Langmuir–Blodgett deposition). By simply injecting a very small amount (1 ml) of ethanol dispersion of sulphonated graphene sheets (GSs) to the hexane/water interface, GSs can be effectively confined at the interface and self-organize into monolayer film with high uniformity and a controllable topographical feature. Multilayered films can also be obtained by layer-by-layer deposition without extra binding agent, demonstrating a cost-efficient, convenient, flexible and controllable approach for high quality ultrathin graphene films.