High-throughput exploration of halide perovskite compositionally-graded films and degradation mechanisms

Shahram Moradi,Vishal Yeddu,Oleksandr Voznyy,Makhsud I Saidaminov,Soumya Kundu,Milad Rezazadeh

doi:10.1038/s43246-022-00235-5

Shahram Moradi, Vishal Yeddu + Show 4 more

Open Access

https://doi.org/10.1038/s43246-022-00235-5

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Abstract

The conventional approach to search for new materials is to synthesize a limited number of candidates. However, this approach might delay or prevent the discovery of better-performing materials due to the narrow composition space explored. Here, we fabricate binary alloy films with a composition gradient in a single shot in less than one minute. We apply this approach to study the stability of halide perovskites. We synthesize all possible binary compositions from MAPbI3 and MAPbBr3 and then study their optical properties, structure, and environmental stability in a high-throughput manner. We find that perovskite alloys experience three different degradation mechanisms depending on halogen content: bromine-rich perovskites degrade by hydration, iodine-rich perovskites by the loss of the organic component, and all other intermediate alloys by phase segregation. The proposed method offers an avenue for discovering new materials and processing parameters for a wide range of applications that rely on compositional engineering.

Highlights

Results and discussionWe chose a slot-die coating method to fabricate compositionally-graded films (CGFs). This method is promising for roll-to-roll fabrication and commercialization of solution-processed materials, including polymer and perovskite solar cells and light-emitting diodes[17,32,33,37]
The conventional approach to search for new materials is to synthesize a limited number of candidates
We show an approach for a synthesis of all possible phases in binary systems in one shot. We achieve this by developing a strategy for the fabrication of compositionally-graded films (CGFs), where the film starts with one composition and gradually transitions to another through alloying

Summary

Results and discussion

We chose a slot-die coating method to fabricate CGFs. This method is promising for roll-to-roll fabrication and commercialization of solution-processed materials, including polymer and perovskite solar cells and light-emitting diodes[17,32,33,37]. We first programmed one pump to decrease its solution supply gradually while the other pump—to increase it This approach led to nonlinear and discontinuous gradient films due to the delayed arrival of second ink as it starts at a low speed. After filling the slot-die head with one ink, we stopped its supply and started supplying the second ink at high speed, simultaneously moving the slot-die along the substrate. This alternated ink supply approach allowed for in situ mixing of two solutions and in situ gradient change of final solution composition and enabled the fabrication of CGFs, as we show below. The PL bandgaps of the CGF follow the absorption bandgap trend (Fig. 2g, f)

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