Developing cost-effective and rational hole transporting materials is critical for fabricating high-performance perovskite solar cells (PSCs) and to promote their commercial endeavor. We have designed and developed pyridine (core) bridging diphenylamine-substituted carbazole (arm) small molecules, named as 2,6PyDANCBZ and 3,5PyDANCBZ. The linking topology of core and arm on their photophysical, thermal, semiconducting and photovoltaic properties were probed systematically. We found that the 2,6PyDANCBZ shows higher mobility and conductivity along with uniform film-forming ability as compared to 3,5PyDANCBZ. The PSCs fabricated with 2,6PyDANCBZ supersede the performance delivered by Spiro-OMeTAD, and importantly also gave improved long-term stability. Our findings put forward small molecules based on core-arm linking topology for cost-effective hole selective layers designing.

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Fossil fuels generate the majority of space heating and hot water demand in the UK, contributing to greenhouse gas emissions and energy security issues. Concerns about the long term availability of traditional fossil fuels are recognised by the UK government and sustainable, low carbon supplies are being actively investigated. One such option in the renewable energy mix is the use of low enthalpy heat, using open loop ground source technology to recover heat from abandoned flooded coal mines. To assess this potential in the South Wales Coalfield we measured annual temperatures and chemistry at sixteen mine water sites. Mean monthly temperatures ranged from 10.3 to 18.6 °C with an overall mean of 13.3 °C, proving their suitability for low enthalpy heat recovery. Collated data shows the geothermal gradient can vary within the South Wales Coalfield. Exothermic chemical reactions within abandoned mine workings can also contribute to the overall temperature of mine waters. Using discharge and temperature data we estimate that 42 MW of potential heating energy could be generated from currently monitored mine water discharges, however historic dewatering data from operational mines suggests that 72 MW could be generated, enough to heat about 6500 homes. The true potential, if new pumping wells were drilled to exploit flooded workings is likely to be much greater. The use of low enthalpy mine water for space heating and hot water indicate a total emission reduction of around 59% and 76% compare to main gas and electricity heating respectively.

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The influence of type and amount of clays present in soils on their properties is well understood. The clays exert their influence through large specific surface area and charges on them. Their effect is mostly exhibited through inter particle bonding and subsequent particle associations. The mineralogical influence of soils in water is well documented. However, the change in soil water system because of presence some of the contaminants can greatly influence the soil behaviour. Some of the changes are due to formation of new compounds due to interactions between the soil and pollutant. The paper reports the effect of interaction of kaolinite mineral with alkali on the index properties of soils from which the geotechnical behaviour can be understood. Detailed X-ray diffraction studies have shown that sodium aluminum silicate hydroxide hydrate (NASH) is formed by clay alkali reactions. The type and amount of formation of the compound is influenced by the concentration of alkali solution. While the compound formed is in smaller quantities with 1 N NaOH solution, significantly high quantity is formed with 4 N NaOH solution. Presence of alumina is shown to play a significant role. It was observed that the formation of sodium aluminum silicate hydroxide hydrate is reduced in the presence of alumina. Specific gravity of contaminated clay soil was reduced which confirms the formation of new compounds. Water adsorption and specific surface area of soil are also influenced due to soil alkali interaction. The changes in the free swell and index properties of soil in the presence of alkali have been explained by the changes in soil fabric and the formation of new compound.

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For the practical application of perovskite solar cells (PSC), it is desirable to have high efficiency, long-term stability, and low manufacturing cost. Therefore, it is required to develop inexpensive and well-performing hole-transporting materials (HTMs). In this study, we synthesized SFXDAnCBZ, which is a new carbazole-based spiro­[fluorene-9,9′-xanthene] (SFX) derivative, where the central core and end-cap units consist of SFX and N3,N6-bis­(di-4-anisylamino)-9H-carbazole (DAnCBZ), respectively, as an efficient and low-cost HTM for PSCs. Photoluminescence quenching at the SFXDAnCBZ/perovskite interface was more effective than at the perovskite/Spiro-OMeTAD (2,2′,7,7′-tetrakis-(N,N-di-p-methoxy-phenyl-amine) 9,9′spiro-bifluorene) interface. We fabricated a PSC with a power conversion efficiency (PCE) of 20.87% under 1 sun illumination (100 mW cm–2) using SFXDAnCBZ as an HTM. This value is comparable to that measured for the benchmark Spiro-OMeTAD. Thus, this result confirms that SFX core-based materials can be a new kind of HTMs for high-efficiency and low-cost PSCs.