Beyond Efficiency: the Challenge of Stability in Mesoscopic Perovskite Solar Cells

Abstract

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.

Long term stability of air processed inkjet infiltrated carbon-based printed perovskite solar cells under intense ultra-violet light soaking

“…The total amount of UV irradiation during the test actually even exceeds the targets for the commercial terrestrial thin-lm cells. 24 The results presented in this work are therefore very promising from the commercialization view point of perovskite solar cells -the technology is clearly not inherently unstable and future developments might lead to market breakthroughs. …”

“…ultra-violet (UV) light which has been identied as one of the key issues for the long term stability of other types of PV systems such as dye-sensitized solar cells (DSSCs), 22,23 and has raised concerns also in the eld of perovskite solar cells. 8,24,25 Hence one batch of inkjet inltrated CPSCs (similar to the cells fabricated in ref. 20) with no encapsulation was initially placed under intense 1.5 Sun UV light illumination in an electronic weather chamber under open circuit conditions with approximately 45% relative air controlled humidity and 40 C temperature of the cells (see details in the ESI †).…”

A stable lead halide perovskite nanocrystals protected by PMMA

“…However, HOIP materials suffer from poor stability under external stresses, especially moisture, heat and light, due to their low formation energy (approximate 0.1-0.3 eV) [11][12][13][14]. Once water approaches the perovskite surface, it prefers to strongly bind Pb cations, and then the structure degrades within only 8.5 ps [15,16].…”

Extending the environmental lifetime of unpackaged perovskite solar cells through interfacial design

“…4,5 Limited shelf as well as operational lifetime have been reported in the early stages of perovskite research and appeared to be one of the major roadblocks towards further driving this technology. 6 The precise degradation mechanism of perovskites in the presence of water is still under discussion. Previous studies have reported the loss of methyl-amine and the formation of yellowish PbI 2 , while more recent studies rather suggest the partially reversible formation of (CH 3 NH 3 ) 4 PbI 6 :H 2 O hydrate complexes as an intermediate step.…”