Ruddlesden–Popper Perovskites with Narrow Phase Distribution for Air‐Stable Solar Cells

Abstract

2D Ruddlesden–Popper perovskites have risen to prominence as stable and efficient photovoltaic materials because of their structural diversity, rich photophysics, and low moisture ingression. However, thin films processed from stoichiometric precursor solutions possess a broad phase distribution of different number of inorganic layers with random crystal orientation, crippling device performance. The effect of methylammonium chloride (MACl) and 3‐amino‐4‐phenolsulfonic acid (APSA) on the fabrication of perpendicularly oriented (PEA)2MA4Pb5I16 films with narrow phase distribution using antisolvent and hot‐casting processing techniques is investigated. MACl plays a critical role in suppressing parasitic n ≤ 2 and 3D‐like phases. APSA performs the dual function of trap passivation and further narrowing phase polydispersity through strong coordination with Pb2+. Ex situ grazing‐incident wide‐angle X‐Ray scattering (GIWAXS) and ultrafast spectroscopic characterization reveal uniformly mixed‐phase distribution with disordered orientation in antisolvent treated films, while additive‐assisted hot‐casting treatment results in oriented, reverse‐graded phase distribution, i.e., small‐n on the film surface and large‐n at the bottom. Arising thin films enable efficient p–i–n solar cells with an efficiency of 14.34%, and a Voc of 1.20 V, retaining 96% initial efficiency after 1440 h under ambient conditions (RH = 50–60%) without encapsulation.

Recent advances in ionic molecules applied in perovskite solar cells

“…19 Chemical structures of BMPBr, 135 EMIFAP, 136 choline bromide, 137 HDZWs, 138 DTPT 140 and APSA. 144 determined by the nature of the materials, a well-matched energy level alignment can be achieved by the utilization of suitable materials. However, considering cost, processibility and stability, there are only a few available candidates for each functional layer.…”

High‐Performing Quasi‐2D Perovskite Photodetectors with Efficient Charge Transport Network Built from Vertically Orientated and Evenly Distributed 3D‐Like Phases

“…It is currently considered as an ideal phase structure for photodetection in prevailing understanding, which is beneficial for energy transfer and charge transfer, which contributes to high‐performing photodetection. [ 15 ] In 2021, Min et al. achieved a record level of R and D * (0.44 A W −1 /3.4 × 10 12 Jones) based on a vertically gradient‐distributed phase structure.…”

“…It is currently considered as an ideal phase structure for photodetection in prevailing understanding, which is beneficial for energy transfer and charge transfer, which contributes to high-performing photo detection. [15] In 2021, Min et al achieved a record level of R and D* (0.44 A W −1 /3.4 × 10 12 Jones) based on a vertically gradient-distributed phase structure. [6] Very recently, Ollearo et al realized a very decent D* of 7.5 × 10 12 Jones via suppressing the thermal charge generation from the low n-phase close to the substrate.…”

Multiple Phase Regulation Enables Efficient and Bright Quasi-2D Perovskite Light-Emitting Diodes

“…6,7 Furthermore, the anisotropy of long-chain organic cations may lead to anisotropic crystals, which is unfavorable for the transport of charge carriers in perovskite films. 8,9 These issues regarding phase distribution and orientation adversely affect the external quantum efficiency (EQE) of LEDs. 10,11 To reduce the nonradiative loss caused by small-n phases and boost the luminescent efficiency of quasi-2D perovskites, substantial efforts have been made by optimizing the distribution of different n phases.…”

“…Quasi-2D Ruddlesden–Popper (RP) perovskites have drawn significant attention due to their excellent optoelectronic properties . The strong quantum and dielectric confinement effects result in a large exciton binding energy, which increases the radiative recombination rate and enhances the photoluminescence quantum yields (PLQYs). , The energy funneling structure promotes rapid localization and recombination of charge carriers, which is favorable for efficient light-emitting diodes (LEDs). , However, during the deposition of quasi-2D perovskite films, because of the random stacking of [PbBr 6 ] 4– sheets and organic spacer cations, small-n phases are unpredictable and excessive, which is likely to generate disordered phase distribution, cause severe exciton energy loss and insufficient energy transfer, and thus decrease the charge transfer efficiency. , Furthermore, the anisotropy of long-chain organic cations may lead to anisotropic crystals, which is unfavorable for the transport of charge carriers in perovskite films. , These issues regarding phase distribution and orientation adversely affect the external quantum efficiency (EQE) of LEDs. , …”