Inorganic hole contacts for perovskite solar cells: Towards high-performance printable solar cells

Organic-inorganic hybrid perovskites have been demonstrated to be efficient light absorbers for solar cells with a power conversion efficiency (PCE) exceed ing 20%, and the low-temperature solution deposition process makes them very suitable for printable solar cells. For most perovskite solar cells, organic materi als such as PEDOT:PSS and Spiro-OMeTAD are the most frequently employed hole transport material (HTM). However, the high acidity and hygroscopicity of PEDOT:PSS make it not good for the long-term stability of the device, and the high price of spiro-OMeTAD as well as its complicated doping process also make it not so attractive for device fabrication. Apart from the organic HTMs, many inorganic materials have also been employed as hole HTMs for perovskite films, such as CuI, CuSCN, NiO, and so on. Compared to the traditional organic HTMs, inorganic HTMs usually have higher mobility and stability, which probably prom ises a better device performance. In this chapter, we will present the recent results on preparation and characterization of inorganic hole HTMs together with their application in perovskite solar cells. Particularly, printed perovskite solar cells with inorganic hole HTMs will be reviewed and discussed.