Organic-inorganic hybrid lead halides as absorbers in perovskite solar cells: a debate on ferroelectricity

Abstract

New photovoltaic materials have been extensively searched for in the last decade for clean and renewable solar energy conversion. Among them, the organic–inorganic hybrid lead halide perovskite solar cell is of current interest to the solar cell community because of its low processing cost, ease of fabrication and high power conversion efficiency. These perovskites show great potential to be photovoltaic absorbers with excellent optoelectronic properties, for example, high absorption coefficient, long charge carrier diffusion length, moderate ambipolar mobilities, tunable bandgap, etc. The unique physical and chemical properties of these materials are based on the crystal structure of the perovskites, named after the mineral form of CaTiO3. Most inorganic materials with a perovskite crystal structure typically show ferroelectric properties. Ferroelectricity in methylammonium lead tri-iodide (MAPbI3), an absorbing material in perovskite solar cells with a perovskite crystal structure, is now a topic of debate. Some theoretical and experimental investigations have shown the presence of a ferroelectric domain in these perovskites, although a lot of controversial results and conclusions also exist in the literature. In this review, notable signs of progress in the theoretical and experimental studies regarding ferroelectricity in organic-inorganic hybrid perovskites are summarized. In addition, future improvements of ferroelectric perovskites are proposed, paving the way towards prospective high-performance flexible and wearable ferroelectric solar cells and optoelectronic devices.

Dynamic structural property of organic-inorganic metal halide perovskite

“…And thus it is required to study the clear picture of both the A-site molecule motions and structural dynamics. (See, recent review paper by one of the authors ( Nandi et al., 2020 ))…”

Stabilizing Mixed Halide Lead Perovskites against Photoinduced Phase Segregation by A-Site Cation Alloying

“…Organic–inorganic hybrid perovskites of the type APbX 3 {A = CH 3 NH 3 + [methylammonium (MA + )], CH­(NH 2 ) 2 + [formamidinium (FA + )], or Cs + ; and X = I – , Br – , or Cl – } have attracted significant attention in the past few years as absorbers in photovoltaic cells − and optoelectronic devices − due to their high absorption coefficient, low exciton dissociation energy, long carrier lifetime, and defect tolerating properties. − The power conversion efficiencies (PCEs) of perovskite-based solar cells (PSCs) have increased almost 7-fold since the first report of a 3.8% PCE in 2009 . Currently, the record high PCE of hybrid perovskites is 25.5% for single-junction solar cells and 29.15% for the highest publicly disclosed perovskite/silicon (Si) tandem .…”

Ferroic Halide Perovskite Optoelectronics

“…Yet, the interpretation of experimental results argues both ferroelectricity and non‐ferroelectricity in CH 3 NH 3 PbI 3 perovskite. [ 3–63 ] This controversy is related to the polarization‐electric hysteresis, the nanoscale domain structure, etc. Consequently, there are also disagreements on the effect of ferroelectricity on photovoltaic action in MHPs, both detrimental effect (e.g., current‐voltage hysteresis) and beneficial effect (e.g., facilitating photogenerated charge carrier dissociation and transport).…”