Jenny Baker

Flexographic printing of graphene nanoplatelet ink to replace platinum as counter electrode catalyst in flexible dye sensitised solar cell

Abstract A semitransparent catalytically active graphene nanoplatelet (GNP) ink was developed suitable for roll to roll printing onto a flexible indium tin oxide substrate at a speed of 0·4 m s−1. Dye sensitised solar cells using this ink as a catalyst demonstrated efficiencies of 2·0%, compared with 2·6% for sputtered platinum. Given further optimisation, GNP inks have the potential to replace chemically reduced or sputtered platinum. This would have the benefit of replacing the chemical reduction or sputtering operations as well as providing potential material cost benefits.

High throughput fabrication of mesoporous carbon perovskite solar cells

The screen printed mesoporous carbon perovskite solar cell has great potential for commercialisation due to its scalable deposition processes and use of inexpensive materials. However, each layer requires long high temperature heating steps to achieve the necessary sintering and porosity, which is very time and energy intensive for large scale production. Near infrared processing is demonstrated here to reduce the heating time of mesoporous layers within a fully printed lead halide perovskite solar cell from 2 hours to 30 seconds. A stabilised efficiency of 11% was achieved by processing in 30 seconds, identical to that of devices heated in 2 hours. For the first time the effect of residual binder in the carbon electrode on the electron lifetime and charge transfer within devices has been investigated. Furthermore cross section EDX mapping of perovskite infiltration provides a greater understanding into the processing requirements of these devices vital to enable commercialisation.

Spray PEDOT:PSS coated perovskite with a transparent conducting electrode for low cost scalable photovoltaic devices

Organic–inorganic lead halide perovskite materials are an attractive candidate for low-cost thin-film photovoltaics but in order to successfully rival other technologies, it is critical to focus research on addressing the potential bottlenecks to commercialisation. The conventional hole transporter spiro-OMeTAD and evaporated gold contact are unsuitable for commercialisation due to the cost. This study introduces a method for fabricating perovskite devices without spiro-OMeTAD. Instead, PEDOT:PSS was applied directly to the perovskite material using a carefully controlled spray process. The water hyphen containing PEDOT:PSS used was spray coated onto the perovskite film with careful drying to provide a 55-nm-thick interlayer between the perovskite and the electrode providing hole collection. XRD analysis showed that by controlled application, it was possible to avoid water-induced perovskite degradation. The device was completed using a previously demonstrated transparent conducting adhesive electrode based on vertically orientated channels of PEDOT:PSS within an acrylic adhesive instead of evaporated gold. Fully fabricated devices gave comparable performance to those without spiro-OMeTAD.

Thin Film Tin Selenide (SnSe) Thermoelectric Generators Exhibiting Ultralow Thermal Conductivity

Tin selenide (SnSe) has attracted much attention in the field of thermoelectrics since the discovery of the record figure of merit (ZT) of 2.6 ± 0.3 along the b-axis of the material. The record ZT is attributed to an ultralow thermal conductivity that arises from anharmonicity in bonding. While it is known that nanostructuring offers the prospect of enhanced thermoelectric performance, there have been minimal studies in the literature to date of the thermoelectric performance of thin films of SnSe. In this work, preferentially orientated porous networks of thin film SnSe nanosheets are fabricated using a simple thermal evaporation method, which exhibits an unprecedentedly low thermal conductivity of 0.08 W m-1 K-1 between 375 and 450 K. In addition, the first known example of a working SnSe thermoelectric generator is presented and characterized.

Screen printed carbon CsPbBr3 solar cells with high open-circuit photovoltage

Screen printed mesoporous carbon solar cells (mC-PSC) are a promising fully printable technology that does not require organic hole conductors, expensive metal contacts or vacuum processing. However, when infiltrated with the archetypal CH3NH3PbI3 perovskite, mC-PSCs show low voltage which limits their use in innovative applications such as indoor light harvesting. Here we investigate both planar (C-PSC) and mesoporous (mC-PSC) carbon cells, based on all-inorganic CsPbBr3. Pure CsPbBr3 is a yellow material with an orthorhombic crystal structure at room temperature and a 2.3 eV band gap, which is not ideal for solar cell applications. However, CsPbBr3 is thermally stable up to over 400 °C and high-voltage planar carbon solar cells, with open circuit voltages of up to 1.29 V and efficiencies up to 6.7% have been reported in the literature. We focus on the effect of the post-annealing temperature on the material properties and photovoltaic activity. XPS and XRD results show a non-linear trend with temperature, with significant improvements in composition between 200 and 300 °C. Both the mesoporous and planar champion devices were obtained after heat processing at 400 °C, reaching PCEs of 8.2% and 5.7% respectively. The average Voc for the planar and mesoporous devices were 1.33 V and 1.27 V respectively with a record 1.44 V for the best mC-PSC.