Beyond Efficiency: the Challenge of Stability in Mesoscopic Perovskite 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. Benefiting from the optimization of perovskite film deposition approaches, the design of new material systems, and the diversity of device concepts, the efficiency of perovskite solar cells (PSCs) has increased from 2.19% in 2006 to a certified 20.1% in 2014, making this the fastest-advancing solar cell technology to date. However, as a photovoltaic technology, which needs to meet the requirements of working under long-term sunlight, PSCs suffer stability concerns for both materials and devices. Evolved from dye-sensitized solar cells (DSSCs), PSCs usually contain a mesoporous electron transporting layer or scaffold layer, a perovskite active layer, a hole transporting layer and a back contact to construct a mesoscopic-structured device. Using interface engineering, mesoscopic PSCs (MPSCs) have obtained exciting stability with a hole-conductor-free printable triple-layer architecture or conventional heterojunction version. Herein, the achievements of mesoscopic solar cells from solid-state DSSCs to MPSCs are outlined and summary of recent progress in the stability of MPSCs is presented. Possible degradation mechanism and solutions are presented and, finally, challenges for the commercialization of this photovoltaic technology are discussed.