Mixed Dimethylammonium/Methylammonium Lead Halide Perovskite Crystals for Improved Structural Stability and Enhanced Photodetection

Abstract

The solvent acidolysis crystallization technique is utilized to grow mixed dimethylammonium/methylammonium lead tribromide (DMA/MAPbBr3) crystals reaching the highest dimethylammonium incorporation of 44% while maintaining the 3D cubic perovskite phase. These mixed perovskite crystals show suppression of the orthorhombic phase and a lower tetragonal‐to‐cubic phase‐transition temperature compared to MAPbBr3. A distinct behavior is observed in the temperature‐dependent photoluminescence properties of MAPbBr3 and mixed DMA/MAPbBr3 crystals due to the different organic cation dynamics governing the phase transition(s). Furthermore, lateral photodetectors based on these crystals show that, at room temperature, the mixed crystals possess higher detectivity compared to MAPbBr3 crystals caused by structural compression and reduced surface trap density. Remarkably, the mixed‐crystal devices exhibit large enhancement in their detectivity below the phase‐transition temperature (at 200 K), while for the MAPbBr3 devices only insignificant changes are observed. The high detectivity of the mixed crystals makes them attractive for visible‐light communication and for space applications. The results highlight the importance of the synthetic technique for compositional engineering of halide perovskites that governs their structural and optoelectronic properties.

Raman spectroscopy in layered hybrid organic-inorganic metal halide perovskites

“…Hybrid organic-inorganic metal halide perovskites (HOIPs) arrived in 2009 as promising materials for photovoltaics with a power conversion efficiency of 3.8% [1], which nowadays exceeds 25% [2]. These materials with already demonstrated extraordinary optoelectronic performance in photovoltaics [3,4], LEDs [5] and photodetectors [6], surpass organic electronics in terms of their figures-of-merit and reach values close to or above Si and semiconductor technology, due to their high optical absorption coefficient, tuneable band-gap, near-unity photoluminescence (PL) quantum yield, low trap densities and excellent excitonic and charge carrier mobility, in addition to their low-cost processability and tuneable crystal structure and composition [3,4,[7][8][9][10][11][12][13][14][15]. Nevertheless, continuous efforts are being made to address several challenges originating from the composition and mixed ionic-electronic conductivity of HOIPs for their successful application in optoelectronic devices, such as the presence of Pb [16,17], low ambient stability (thermal stress, light or oxygen/moisture) [15,[18][19][20], or ion migration under operation [10,18,[21][22][23].…”

“…For this purpose, Raman spectroscopy has shown to be a non-destructive, accessible, and sensitive technique for monitoring simultaneously the structural changes related to the rearrangement of the inorganic cage and A-site cations. Indeed, in the case of 3D HOIPs, Raman spectroscopy has been used to determine phase transition origin and temperature onset [11,[43][44][45][46], to probe local strain [9,47], and to check the material's degradation [48][49][50][51], composition [11,[52][53][54], and quality in terms of crystallinity and polymorphs [44,55,56]. In this review, we focus our attention on the vibrational properties of 2D HOIPs and how Raman spectroscopy can help to disentangle the complexity of these materials.…”

Suppression of Phase Transitions in Perovskite Thin Films through Cryogenic Electron Beam Irradiation

“…Besides, Figure d show the complete suppression of the phase transition down to 85 K in the MAPbI 3 film irradiated at 5 keV. Mixed A-site cations were previously reported to suppress phase transitions; however, this suppression occurred only when the larger-sized DMA was incorporated in MAPbBr 3 . In the mixed compounds, a random distribution of DMA causes a different degree of framework distortion, resulting in a multiwell potential for the MA cation and causing the frustration and suppression of the phase transitions .…”

“…The phase transitions were completely suppressed with 21% DMA incorporation, which was attributed to the enhanced disordered of MA . Recently, a solvent acidolysis crystallization technique was utilized to incorporate 44% DMA into MAPbBr 3 while maintaining its 3D cubic structure . The resultant mixed perovskite exhibited the suppression of the orthorhombic phase and a lower temperature for the transition from the tetragonal phase to the cubic phase due to the MA cation dynamics …”

Current state-of-the-art characterization methods for probing defect passivation towards efficient perovskite solar cells

“…Hence, various passivation strategies have so far been successfully applied to improve the efficiency and stability of PSCs. These methods include the introduction of additives, interface modication, component regulation, solvent engineering, single-crystal engineering, [71][72][73] and electrochemical deposition. [74][75][76][77] The passivation route relies on applying certain chemicals to react with surface components for deactivating their electronic or chemical activities.…”