Chemical Approaches to Addressing the Instability and Toxicity of Lead–Halide Perovskite Absorbers

Abstract

The impressive rise in efficiencies of solar cells employing the three-dimensional (3D) lead-iodide perovskite absorbers APbI (A = monovalent cation) has generated intense excitement. Although these perovskites have remarkable properties as solar-cell absorbers, their potential commercialization now requires a greater focus on the materials' inherent shortcomings and environmental impact. This creates a challenge and an opportunity for synthetic chemists to address these issues through the design of new materials. Synthetic chemistry offers powerful tools for manipulating the magnificent flexibility of the perovskite lattice to expand the number of functional analogues to APbI. To highlight improvements that should be targeted in new materials, here we discuss the intrinsic instability and toxicity of 3D lead-halide perovskites. We consider possible sources of these instabilities and propose methods to overcome them through synthetic design. We also discuss new materials developed for realizing the exceptional photophysical properties of lead-halide perovskites in more environmentally benign materials. In this Forum Article, we provide a brief overview of the field with a focus on our group's contributions to identifying and addressing problems inherent to 3D lead-halide perovskites.

High‐Performance Perovskite Solar Cells with Enhanced Environmental Stability Based on a (p‐FC6H4C2H4NH3)2[PbI4] Capping Layer

“…[40] Since the surface energy tends to decrease spontaneously, this simulation result also indicates that when the bulky cations contact with the surface of a 3D perovskite, the formation of layered perovskite is kinetically favorable. It turns out that the (FPEA) 2 PbI 4 having the lowest surface energy is the most stable one out of the three.…”

“…This was corroborated by the report from Niu et al that remarkable long-term ambient stability was achieved with a t 80 lifetime exceeding 2880 h without encapsulation. [40] [32] Recently, we used an aliphatic fluorinated amphiphilic cation, 1,1,1-trifluoroethyl ammonium iodide (FEAI), to enhance, at the same time, the stability and performance of the PSCs.…”

Decreasing the electronic confinement in layered perovskites through intercalation

“…For example, the n = 3 2D Pb–I perovskite exhibits sufficiently low E g and E b values to absorb sunlight and generate photocurrent in a solar cell, while hydrophobic organic layers provide enhanced moisture resistance. 22,23 Owing to the greater stability and structural diversity of the layered framework compared to the 3D perovskite, we investigated how the common n = 1 Pb–I perovskites can be modified to mimic the optoelectronic properties of their 3D congeners.…”

Large Band Gap Narrowing and Prolonged Carrier Lifetime of (C4H9NH3)2PbI4 under High Pressure

“…The excellent photo voltaic performance of 3D OIHPs is contributed by their efficient light absorption, modest charge-carrier mobility, and long carrier lifetime-prompted long diffusion length. [13,14] Organic and inorganic layers stack alternatively in the crystal, which can be treated as a quantum-well-like structure. Therefore, other kinds of new organic-inorganic halide perovskites with superior properties are highly desirable for further applications.…”