The Role of Pioneering Hole Transporting Materials in New Generation Perovskite Solar Cells

Despite the impressive progresses, perovskite solar cells (PSCs) employing operationally instable organic hole transporting layers (HTLs) are still far from the upscaling applications. Therefore, the development of new sustainable materials to meet the commercialization requirements is of great urgency. In addition, the high cost resulting from the complex production conditions of organic HTL materials is another limiting factor that must be overcome in the way of commercialization. Although various structures and types of HTL materials have been reported in this context, inorganic-based materials have attracted the greatest attention both in terms of low-cost and long-term stability. However, inorganic HTL-based cells have not yet reached the efficiency values of organic HTL-based cells. In this mini Review, it is aimed to evaluate the alternative HTL materials only performing a destructive role in n-i-p architecture in terms of cell performance, stability, and cost. Hereof, a general evaluation of the HTL materials reported in the literature has been made and the effects of these materials on the cell performance have been elaborated and discussed.