Understanding the interplay of stability and efficiency in A-site engineered lead halide perovskites

Abstract

Organic–inorganic hybrid lead halide perovskites have gained significant attention as light-harvesting materials in thin-film photovoltaics due to their exceptional optoelectronic properties and simple fabrication process. The power conversion efficiency of perovskite solar cells (PSCs) has surged beyond 25% in a short time span. Their transition to commercial market is a “work in progress” due to limited long-term operational stability and the persisting environmental concern due to the presence of lead. Comprehensive investigations on the interplay of material composition and interfacial effects on the device performance of PSCs based on methylammonium lead iodide have shown the crucial role of an A-site cation in incipient deterioration of the material through external stimuli (moisture, light, oxygen, or heat). Consequently, a partial or complete replacement of A-site cations by up to four isoelectronic substituents has resulted in many new perovskite compositions. The correlations between the chemical composition and the optoelectronic properties are, however, not always easy to determine. A-site cation management is governed by stability and charge neutrality of the lattice, and the choices include Cs+-cations and organic cations such as CH3NH3+ or CH(NH2)2+ and combinations thereof. Since the size of the cations is an important structural parameter, an adequate compositional engineering of the A-site could effectively optimize the stability by reducing non-radiative defect sites and enhancing carrier lifetimes. This Perspective reflects on the experimental strategies for A-site cation management and their direct impact on the stability and device performance. It also highlights the opportunities and challenges for further research and industrial commercialization of PSCs.

Single- or double A-site cations in A3Bi2I9 bismuth perovskites: What is the suitable choice?

“…In addition to this, exciting optoelectronic properties such as suitable and tuneable bandgap [3], long charge-carrier lifetimes [4,5], relatively low recombination activity at interfaces [6,7], sufficiently high mobilities of both charge carriers, and high defect-tolerance [8], have enabled the application of perovskite materials in various optoelectronic devices. Nevertheless, such high-performing perovskite devices are not always compatible with sufficient durability of the device, which is mainly affected by external factors like moisture, light, heat, and intrinsic factors such as ion migration, defects, and hydrophilic organic cations [9]. This leads to the degradation of the photoactive perovskite material to non-photoactive lead iodide which is inherently toxic [10].…”

“…Efforts have been made to improve the stability via interface engineering, compositional engineering, development of multi-dimensional (2D + 3D) perovskites, etc. [9,[11][12][13]. Among all these approaches, compositional engineering has been at the forefront of research efforts as it not only helps to develop a robust perovskite composition but also helps in tuning its optoelectronic properties [9,14,15].…”

“…[9,[11][12][13]. Among all these approaches, compositional engineering has been at the forefront of research efforts as it not only helps to develop a robust perovskite composition but also helps in tuning its optoelectronic properties [9,14,15]. For instance, the replacement of the methylammonium (MA + ) cation in MAPbI 3 with formamidinium (CH(NH 2 ) 2 + , FA + ) to form FAPbI 3 simultaneously increases thermal stability up to 150 °C and reduces the bandgap (E g ) from 1.55 to 1.47 eV enabling a wider absorption of the solar spectrum [16,17].…”

Highly Reproducible Fabrication of Perovskite Films with an Ultrawide Antisolvent Dripping Window for Large‐Scale Flexible Solar Cells

“…Among numerous organic–inorganic hybrid perovskites, (CsPbI 3 ) 0.05 [(FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.17 ] 0.95 is the most promising material due to its superior photovoltaic performance and the stability. [ 7–10 ]…”

“…Among numerous organic-inorganic hybrid perovskites, (CsPbI 3 ) 0.05 [(FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.17 ] 0.95 is the most promising material due to its superior photovoltaic performance and the stability. [7][8][9][10] Although various deposition methodologies have been used to fabricate the perovskite films, the one-step spin-coating deposition assisted by an antisolvent is still regarded as an efficient and widely accepted approach. [11,12] Nevertheless, the reproducibility of high-quality perovskite films highly depends on the skilled and experienced operator.…”