How machine learning can help select capping layers to suppress perovskite degradation

Abstract

Environmental stability of perovskite solar cells (PSCs) has been improved by trial-and-error exploration of thin low-dimensional (LD) perovskite deposited on top of the perovskite absorber, called the capping layer. In this study, a machine-learning framework is presented to optimize this layer. We featurize 21 organic halide salts, apply them as capping layers onto methylammonium lead iodide (MAPbI3) films, age them under accelerated conditions, and determine features governing stability using supervised machine learning and Shapley values. We find that organic molecules’ low number of hydrogen-bonding donors and small topological polar surface area correlate with increased MAPbI3 film stability. The top performing organic halide, phenyltriethylammonium iodide (PTEAI), successfully extends the MAPbI3 stability lifetime by 4 ± 2 times over bare MAPbI3 and 1.3 ± 0.3 times over state-of-the-art octylammonium bromide (OABr). Through characterization, we find that this capping layer stabilizes the photoactive layer by changing the surface chemistry and suppressing methylammonium loss.

Self‐Driven Multistep Quantum Dot Synthesis Enabled by Autonomous Robotic Experimentation in Flow

“…Generally, experimentation strategies with high reliance on user guidance and operation, require increased time commitment and level of expertise. Recent advances in AI, including deep neural networks (DNN) and reinforcement learning, for rapid chemical space exploration, [49][50][51][52][53][54][55][56][57][58][59][60][61] provide an exciting opportunity to reshape the development and on-demand manufacturing of colloidal nanomaterials. Consequently, a number of self-optimizing microfluidic reactors have been developed to take advantage of continuous material exploration in a low chemical consumption system.…”

Effects of All‐Organic Interlayer Surface Modifiers on the Efficiency and Stability of Perovskite Solar Cells

“…Among various techniques developed, introducing relatively bulkier, more hydrophobic organic moieties endowed with specific functional groups on top of the HPs layer has become one of the primary solutions to address the intrinsic chemical instability and defect states of the material. [27][28][29] Notably, such approach often involves the use of hybrid organic-inorganic salts with the cation being ammonium-based molecules (e. g., n-butylammonium, [30,31] 4hydroxybutan-1-aminium, [32] 2-phenylethylammonium, [24,33] 4-(carboxymethyl)-1H-imidazol-3-ium, [34] and 1-naphthylmethylammonium), [35] while the anion being the halides, in particular iodide. [30,[36][37][38][39][40] The relatively soft ionic character of HPs, in combination with the use of solution processing techniques, unavoidably generates a substantial amount of ionic defects at the materials surfaces.…”

“…Being Lewis bases, halide anions can bind to the undercoordinated Pb 2 + present on HPs surface by donating their electron lone pairs, forming coordinative acid-base complexes, which then passivate the defect sites. [28,29] However, they are also known to be relatively reactive. For example, iodide ion readily transforms to the elemental iodine, capable of forming triiodide complex both in solution and solid states.…”

“…Of particular interest, major advances have been made in the stabilization of the materials’ crystal phases, [22,23] as well as management of their defect density levels (both in the bulk and at the interfaces), [24–27] which lead to compositions and devices with enhanced operational stability towards external stressors, such as moisture, oxygen and heat. Among various techniques developed, introducing relatively bulkier, more hydrophobic organic moieties endowed with specific functional groups on top of the HPs layer has become one of the primary solutions to address the intrinsic chemical instability and defect states of the material [27–29] . Notably, such approach often involves the use of hybrid organic‐inorganic salts with the cation being ammonium‐based molecules (e. g., n ‐butylammonium, [30,31] 4‐hydroxybutan‐1‐aminium, [32] 2‐phenylethylammonium, [24,33] 4‐(carboxymethyl)‐1H‐imidazol‐3‐ium, [34] and 1‐naphthylmethylammonium), [35] while the anion being the halides, in particular iodide [30,36–40] …”

“…In this regard, post‐treatment with halide‐containing organic salts has proven to be effective. Being Lewis bases, halide anions can bind to the under‐coordinated Pb 2+ present on HPs surface by donating their electron lone pairs, forming coordinative acid‐base complexes, which then passivate the defect sites [28,29] . However, they are also known to be relatively reactive.…”