The growth of epitaxial semiconductors and oxides has long since revolutionized the electronics and optics fields, and continues to be exploited to uncover new physics stemming from quantum ...interactions. While the recent emergence of halide perovskites offers exciting new opportunities for a range of thin‐film electronics, the principles of epitaxy have yet to be applied to this new class of materials and the full potential of these materials is still not yet known. In this work, single‐domain inorganic halide perovskite epitaxy is demonstrated. This is enabled by reactive vapor phase deposition onto single crystal metal halide substrates with congruent ionic interactions. For the archetypical halide perovskite, cesium tin bromide, two epitaxial phases, a cubic phase and tetragonal phase, are uncovered which emerge via stoichiometry control that are both stabilized with vastly differing lattice constants and accommodated via epitaxial rotation. This epitaxial growth is exploited to demonstrate multilayer 2D quantum wells of a halide‐perovskite system. This work ultimately unlocks new routes to push halide perovskites to their full potential.
Single‐domain halide perovskite heteroepitaxy is demonstrated and multiple epitaxial phases of archetypical halide perovskite are uncovered via stiochiometry control. The epitaxial growth is further exploited to demonstrate multilayer 2D quantum wells of a halide‐perovskite system and can ultimately enable their full potential in many emerging applications.
Tin‐Oxide Perovskites
In article number 2200964, Non Thongprong, Thidarat Supasai, Nopporn Rujisamphan, and co‐workers presented the pseudohalide salt of sodium tetrafluoroborate, whose anions have a ...higher electronegativity than other halide salts, with the potential to passivate the surface of tin oxide while enhancing the optoelectronic properties of a perovskite film. The current study presents a facile and effective method for enhancing the moderate thermal stability and performance of solar cell devices.
Organic–inorganic perovskite solar cells (PSCs), which have good environmental durability, are of great interest for practical applications. In this work, we show that a solution-processed MoO x ...layer acts as a buffer layer against high moisture stress to suppress defects in the perovskite and as a hole transport layer. The inversion of the photoinduced charge migration behaviors, that is, the electron preferentially moving toward the surface when MoO x is directly deposited onto the perovskite, is found to cause a significant loss in device functionality. The deposition of MoO x onto spiro-OMeTAD results in a lower photocurrent density–voltage (J–V) hysteresis behavior, a greatly enhanced electrical conductivity, and a significantly stabilized power conversion efficiency (PCE) when compared with those of devices without the MoO x layer. More importantly, the PCEs of the MoO x -based devices are retained at over 85% of their initial value, while only 75% is retained for a reference cell. This work highlights the facial fabrication approach of the solution-based MoO x layer and provides experimental evidence of the photogenerated charge migration behaviors on the perovskite/MoO x interface. This information would be beneficial for the further design and development of PSC technology.
In article number 1701003, Richard R. Lunt and co‐workers demonstrate the controllable epitaxial growth of single‐crystal halide perovskites on low cost ionic crystal substrates investigated by in ...situ real‐time diffraction. Such growth is achieved by reactive vapor‐phase deposition enabling precise control for tuning epitaxial phases, demonstrating multilayer quantum wells, and providing a new route to uncover the full potential of halide perovskites.
We demonstrate a functional method to achieve surface passivation and construct a two-dimensional (2D) layer on a three-dimensional (3D) perovskite, eliminating the need for subsequent annealing ...steps. A key process is the integration of a single methylammonium lead iodide (MAPbI3) crystal with butylammonium iodide (BAI) in tetrahydrofuran. Density functional theory calculations reveal that the synergy between BA+ cations and Pb–I octahedral structures enables the formation of a distinct 2D layered framework. MA+ and BA+ exhibit adsorption energies of −5.519 and −5.925 eV, respectively, at MA vacancies on the perovskite surface. This finding indicates that BAI passivation induces surface-healing effects, increasing surface and device stability. The I– components of BAI also replace imperfections at the perovskite interface, affording considerably reduced deep-level anomalies and mitigating nonradiative recombination. This theoretical perspective is supported experimentally via X-ray photoelectron spectroscopy and glow discharge optical emission spectroscopy. BAI passivation and 2D-BA2PbI4 capping lowers work functions for 3D perovskite surfaces, registering at approximately 0.158 and 0.173 eV, respectively, which are lower than those of the control 3D film. Within the 2D/3D perovskite configuration, 2D-BA2PbI4 capping considerably increases the open-circuit voltage in solar cells. In comparison, devices with BAI-enhanced interfaces show improved durability with promise for solar cell applications.
PDF
