Dye-sensitized solar cells (DSSCs) have aroused great interest and been regarded as a potential renewable energy resource among the third-generation solar cell technologies to fulfill the 21 century global energy demand. DSSCs have notable advantages such as low cost, easy fabrication process and being eco-friendly in nature. The progress of DSSCs over the last 20 years has been nearly constant due to some limitations, like poor long-term stability, narrow absorption spectrum, charge carrier transportation and collection losses and poor charge transfer mechanism for regeneration of dye molecules. The main challenge for the scientific community is to improve the performance of DSSCs by using different approaches, like finding new electrode materials with suitable nanoarchitectures, dyes in composition with promising semiconductors and metal quantum dot fluorescent dyes, and cost-effective hole transporting materials (HTMs). This review focuses on DSSC photo-physics, which includes charge separation, effective transportation, collection and recombination processes. Different nanostructured materials, including metal oxides, oxide perovskites and carbon-based composites, have been studied for photoanodes, and counter electrodes, which are crucial to achieve DSSC devices with higher efficiency and better stability.

Methylammonium lead tri‐iodide (MAPbI3) hybrid perovskite powder is successfully synthesized using a two‐step antisolvent precipitation (TSAP) method. This MAPbI3 powder is compressed to make a pellet, on the surface of which is designed an ammonia sensor that operates at room temperature. The tetragonal structure and porous morphology with well‐connected perovskite grains of the pellet are studied using X‐ray diffraction and scanning electron microscopy techniques. This is the first report of air‐stable, substrate free, and robust ammonia sensors based on perovskite pellets based in which the perovskite powder is synthesized with an unreported TSAP method. Gas‐sensing measurements show responsivity of 200% in 0.3 s and excellent recovery in 3.6 s upon exposure to 10 ppm ammonia gas. The sensor shows excellent structural and morphological ammonia sensing reversibility. A MAPbI3 pellet stored in ambient air with a relative humidity of 20–45% exhibits a lifetime of 60 d. These results successfully demonstrate new insights for environmentally friendly low‐cost manufacturing of highly sensitive robust perovskite ammonia sensors.

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