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

Environmental stability of perovskite solar cells (PSCs) can be improved by a thin layer of low-dimensional (LD) perovskite sandwiched between the perovskite absorber and the hole transport layer (HTL). This layer, called ‘capping layer,’ has mostly been optimized by trial and error. In this study, we present a machine-learning framework to rationally design and optimize perovskite capping layers. We ‘featurize’ 21 organic halide salts, apply them as capping layers onto methylammonium lead iodide (MAPbI3) thin films, age them under accelerated conditions combining illumination and increased humidity and temperature, and determine features governing stability using random forest regression and SHAP (SHapley Additive exPlanations). We find that a low number of hydrogen-bonding donors and a small topological polar surface area of the organic molecules correlate with increased MAPbI3 film stability. The top performing organic halide salt, 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 morphological and synchrotron-based structural characterization, we found that this capping layer consists of a Ruddlesden-Popper perovskite structure and stabilizes the photoactive layer by “sealing off” the grain boundaries and changing the lead surface chemistry, through the suppression of lead (II) iodide (PbI2) formation and methylammonium loss.

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

Nature Communications ◽

10.1038/s41467-020-17945-4 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Noor Titan Putri Hartono ◽

Janak Thapa ◽

Armi Tiihonen ◽

Felipe Oviedo ◽

Clio Batali ◽

...

Keyword(s):

Machine Learning ◽

Perovskite Solar Cells ◽

Supervised Machine Learning ◽

Environmental Stability ◽

Lead Iodide ◽

Film Stability ◽

Organic Halide ◽

Capping Layer ◽

Shapley Values ◽

Low Dimensional

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.

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Degradation mechanism of hybrid tin-based perovskite solar cells and the critical role of tin (IV) iodide

Nature Communications ◽

10.1038/s41467-021-22864-z ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Luis Lanzetta ◽

Thomas Webb ◽

Nourdine Zibouche ◽

Xinxing Liang ◽

Dong Ding ◽

...

Keyword(s):

Degradation Mechanism ◽

Critical Role ◽

Perovskite Solar Cells ◽

Hole Transport ◽

Transport Layer ◽

Environmental Stability ◽

Hole Transport Layer ◽

Future Design ◽

Cyclic Degradation ◽

Stability Issues

AbstractTin perovskites have emerged as promising alternatives to toxic lead perovskites in next-generation photovoltaics, but their poor environmental stability remains an obstacle towards more competitive performances. Therefore, a full understanding of their decomposition processes is needed to address these stability issues. Herein, we elucidate the degradation mechanism of 2D/3D tin perovskite films based on (PEA)0.2(FA)0.8SnI3 (where PEA is phenylethylammonium and FA is formamidinium). We show that SnI4, a product of the oxygen-induced degradation of tin perovskite, quickly evolves into iodine via the combined action of moisture and oxygen. We identify iodine as a highly aggressive species that can further oxidise the perovskite to more SnI4, establishing a cyclic degradation mechanism. Perovskite stability is then observed to strongly depend on the hole transport layer chosen as the substrate, which is exploited to tackle film degradation. These key insights will enable the future design and optimisation of stable tin-based perovskite optoelectronics.

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Investigation of Various Commercial PEDOT:PSS (Poly(3,4-Ethylenedioxythiophene)Polystyrene Sulfonate) As A Hole Transport Layer in Lead Iodide Based Inverted Planar Perovskite Solar Cells

10.21203/rs.3.rs-269998/v1 ◽

2021 ◽

Author(s):

Hamed Moeini Alishah ◽

Fatma Pinar Gokdemir Choi ◽

Serap Gunes

Keyword(s):

Solar Cells ◽

High Performance ◽

Low Cost ◽

Perovskite Solar Cells ◽

Vital Role ◽

Hole Transport ◽

Transport Layer ◽

Hole Transport Layer ◽

Lead Iodide ◽

Very High

Abstract Inverted-type perovskite solar cells have drawn remarkable attention due to solution-processable, straightforward configuration, low-cost processing, and manufacturing at very high throughput, even on top of flexible materials. The hole transport material (HTM) plays a vital role to achieve high performance in inverted type of perovskite solar cells. Herein, we report on the effect of different commercial PEDOT: PSS such as PH 1000, PH 500, P VP AI, and P T2, on the performance of CH3NH3PbI3 based planar perovskite solar cells.

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