Revealing the Transient Formation Dynamics and Optoelectronic Properties of 2D Ruddlesden‐Popper Phases on 3D Perovskites

Abstract

Using in situ photoluminescence measurements during the spin-coating and annealing steps, we probed the formation of 2D layers on 3D triple cation perovskite films comparing phenylethylammonium and 2-thiophenemethylammonium iodide bulky cations. We elucidate the formation mechanisms of the surface layers for both cases and reveal two regimes during 2D layer formation: a kinetic-driven and a thermodynamic-driven process. These driving forces result in different compositions of the 2D/3D interface for each treatment; namely, different ratios of pure 2D (n = 1) and quasi-2D (n > 1) structures. We show that a higher ratio of quasi-2D phases is more beneficial for device performance, as pure-2D layers may hamper current extraction. Due to a more evenly distributed formation energy profile among 2D and quasi-2D phases, highly concentrated 2-thiophenemethylammonium iodide appears to be more suited for effective surface passivation than its phenylethylammonium analog.

Tiny spots to light the future: advances in synthesis, properties, and application of perovskite nanocrystals in solar cells

“…By varying the A, B, and X species, it is possible to obtain a plethora of different perovskite compositions, allowing fine control of the MHP structural, optoelectronic and photophysical properties. 2,[35][36][37][38][39][40] Another method to control the MHP's properties is changing its dimensionality rather than composition. Going from bulk 3D to 0D quantum dots (QD) the energy band structure changes from continuous to discrete (i.e., quantized) (Fig.…”

“…By varying the A, B, and X species, it is possible to obtain a plethora of different perovskite compositions, allowing fine control of the MHP structural, optoelectronic and photophysical properties. 2,35–40…”

Vapor-Deposited n = 2 Ruddlesden–Popper Interface Layers Aid Charge Carrier Extraction in Perovskite Solar Cells

“…We observe that deposition from solvents such as IPA produces a mix of n = 2 and n = 1 phases at the surface of the films, either by progressive dimensional reduction or induced by variations in concentration of the bulky cations at the surface, as has been suggested in previous reports. 5,9 We achieve the highest median power conversion efficiency (PCE) with vapor deposition of the capping layer. Our work demonstrates the potential of vapor deposition for interface passivation of MHP devices, a route to selectively form an n = 2 capping layer, and it provides fundamental insights toward the development of more efficient and reliable perovskite solar cells.…”

“…We select this composition due to its popularity in 3D/2D perovskite literature and its interfacial variations upon exposure to phenetylammonium iodide (PEAI). 5,6,15,20,23 We deposit PEAI via solution (labeled PEAI sol) on a CsFAMA perovskite surface using a concentration of 5 mg mL −1 in IPA. We deposit PEAI via vapor (PEAI vap) using thermal evaporation.…”

“…9 The presence of polar solvents that can dissolve A-site cations in the ABX 3 3D perovskite structure, such as IPA, have been associated with a more rapid transformation to the n = 1 configuration. 5,9 Furthermore, the speed and type of conversion has also proven to be dependent on the perovskite composition used and on the concentration of the bulky cation in solution. 5 In this work we use a triple cation composition with double halide, on which we perform a static spin coat of the PEAI cation.…”