Solid-state mesoscopic solar cells

Over the past five years, the rapid emergence of a new class of solar cell based on mixed organic–inorganic halide perovskite semiconductors has captured the attention of scientists and researchers in the field of energy conversion. Recently, a new generation of photovoltaic converters, mesoscopic solar cells (MSCs), has attracted more and more attention due to their high energy conversion efficiencies as well as the advantages of low material cost and simple fabrication process, such as dye-sensitized solar cells (DSSCs) and mesoscopic perovskite solar cells (MPSCs). Since being reported by M. Grätzel group in 1991, DSSC has been paid intensive attention in the last twenty years. In 1998, M. Grätzel group firstly reported a solid-state organic hole-transporting-material (HTM) 2,2,7,7-tetrakis( N , N -di-pmethoxy-phenylamine)-9,9-spirobifluorene (spiro-OMeTAD) to replace the conventional liquid-state electrolyte and developed a solid-state DSSC (ss-DSSC). From 1998 to 2011, the PCE of ss-DSSC increased steadily from 0.74% to 7.2%, but still much lower than that obtained by liquid-state electrolyte based DSSCs. In late 2012, a breakthrough was made by using CH3NH3 PbI3 (MAPbI3) perovskite nanocrystals as the light absorber to fabricate a solid-state MPSC with a PCE of up to 9.7%. Such MPSCs employ similar device architecture and fabrication process to ss-DSSCs, thus also have the advantages of low material cost and simple fabrication process, which makes perovskite solar cells (PSCs) one of the most promising low-cost photovoltaic technologies. From then on, the research focus on solid-state MSCs began to transfer from DSSCs to MPSCs. To date, the PCE increased to a certified 22.1%. These results not only inspired the research on this photovoltaic technology but also attracted much attention from industry. However, as a promising photovoltaic technology that needs to be applied in outdoor and long-term working condition, PSCs still suffer the concerns of stability at current stage, which is associated with the perovskite absorbers, device components, interface properties, and so on.