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Since its invention in 2009, Perovskite solar cells (PSCs) has attracted great attention because of its low cost, numerous options of efficiency enhancement, ease of manufacturing and high-performance. Within a short span of time, the PSC has already outperformed thin-film and multicrystalline silicon solar cells. A current certified efficiency of 25.2% demonstrates that it has the potential to replace its forerunner generations. However, to commercialize PSCs, some problems need to be addressed. The toxic nature of lead which is the major component of light absorbing layer, and inherited stability issues of fabricated devices are the major hurdles in the industrialization of this technology. Therefore, new researching areas focus on the lead-free metal halide perovskites with analogous optical and photovoltaic performances. Tin being nontoxic and as one of group IV(A) elements, is considered as the most suitable alternate for lead because of their similarities in chemical properties. Efficiencies exceeding 13% have been recorded using Tin halide perovskite based devices. This review summarizes progress made so far in this field, mainly focusing on the stability and photovoltaic performances. Role of different cations and their composition on device performances and stability have been involved and discussed. With a considerable room for enhancement of both efficiency and device stability, different optimized strategies reported so far have also been presented. Finally, the future developing trends and prospects of the PSCs are analyzed and forecasted.

The fabrication and characterization of a novel co-planar humidity sensor based on organic semiconducting material, vanadyl phthalocyanine (VOPc), is presented in this paper. Here we examine the effect of different humidity conditions on the capacitive and resistive response of VOPc thin films in the Al/VOPc/Pt co-planar structure. The two asymmetric electrodes, aluminum (Al) and platinum (Pt), were deposited through the photolithography technique. Thin films of VOPc were spun-cast on the glass substrate with primarily deposited asymmetric metal electrodes, from a solution of 30 mg ml−1 in chloroform at 3000 rpm. The gap between the electrodes was 17 µm. A 100-fold increase was observed in the capacitance of the VOPc sensing material with an elevation of relative humidity level. The resistance of the sensor reduced from 2.9 GΩ to 2.1 MΩ with increasing level of humidity. The VOPc thin film has been analyzed by x-ray diffraction as well as atomic force microscopy in order to get structural and morphological information on the sample. Adequate sensing properties such as enough sensitivity, good selectivity, linearity and reasonable response and recovery times have been obtained. The humidity-dependent properties of the sensor make it a good match for its potential application in commercial hygrometers.

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