Tin perovskites have emerged as promising alternatives to toxic lead perovskites in next-generation photovoltaics, but their poor environmental stability remains an obstacle towards more competitive performances. Therefore, a full understanding of their decomposition processes is needed to address these stability issues. Herein, we elucidate the degradation mechanism of 2D/3D tin perovskite films based on (PEA)0.2(FA)0.8SnI3 (where PEA is phenylethylammonium and FA is formamidinium). We show that SnI4, a product of the oxygen-induced degradation of tin perovskite, quickly evolves into iodine via the combined action of moisture and oxygen. We identify iodine as a highly aggressive species that can further oxidise the perovskite to more SnI4, establishing a cyclic degradation mechanism. Perovskite stability is then observed to strongly depend on the hole transport layer chosen as the substrate, which is exploited to tackle film degradation. These key insights will enable the future design and optimisation of stable tin-based perovskite optoelectronics.

Hybrid organic lead trihalide perovskites continue to generate significant interest for use in optoelectronic devices such as solar cells and light-emitting devices. However, the toxicity of lead is considered one of the main obstacles to the commercialization of this technology. Although challenging, the replacement of lead by tin is currently the most promising alternative. Herein, we explore a class of low-dimensional, lead-free perovskite materials (2D (PEA)2SnI x Br4–x , where PEA ≡ C6H5CH2CH2NH3 +) with tunable optical properties in the visible region of the spectrum. Specifically, we show that 2D (PEA)2SnI4 perovskite exhibits superior photoluminescence properties to conventional 3D CH3NH3SnI3 and that (PEA)2SnI4 can act as a sensitizer on mesoporous TiO2. We go on to demonstrate visible (∼630 nm) electroluminescence from a device employing a (PEA)2SnI4 emitter sandwiched between ITO/PEDOT:PSS and F8/LiF/Al as hole and electron injection electrodes, respectively. These devices reach a luminance of 0.15 cd/m2 at 4.7 mA/cm2 and an efficacy of 0.029 cd/A at 3.6 V. This proof-of-principle device indicates a viable path to low-dimensional, lead-free perovskite optoelectronics.

Nickel oxide (NiOx) has exhibited great potential as a hole transport layer (HTL) for fabricating efficient and stable perovskite solar cells (PSCs). However, it has been greatly limited by its fabrication and manipulation process. In this work, a simple processing method on an ultrathin electrochemical mesoporous NiOx film manipulated by controllable ultraviolet/ozone (UVO) treatmentis employed; the duration of UVO treatment on the NiOx film significantly affects the photovoltaic properties of the PSCs. When the exposure duration increases, the wettability, electrical conductivity, nonstoichiometry, and valence band energy of the NiOx film are improved with varying degrees. Besides, the perovskite grain size, recombination resistance at the perovskite/NiOx interface, and build‐in potential of the device also increase, resulting in higher short‐circuit current density (JSC) and open‐circuit voltage (VOC). Combining these factors together, an optimal exposure time of UVO treatment on the NiOx film has been achieved at 5 min, which results in a significantly high performance with an efficiency of 19.67%, large VOC (>1.1 V), and JSC (>23 mA cm−2). Furthermore, the experimental results are coincide well with simulation results on the different corresponding subjects. Hopefully, this work could facilitate material manipulation toward scalable, high efficiency, and stable solar cells.

Methylammonium lead halide perovskites have attracted enormous attention due to their remarkable physical properties and potential for numerous (opto)electronic applications. Here, high-performance photodetectors based on CH3NH3PbI3 (MAPbI3)/CdS heterostructures, are demonstrated. The resulting self-powered MAPbI3/CdS photodetectors show excellent operating characteristics including a maximum detectivity of 2.3×10 11 Jones, responsivity of 0.43 A/W (both measured at 730 nm) and temporal response time of <14 ms. The mechanisms of charge separation and transport at the interface of the MAPbI3/CdS junction were investigated via conductive and photoconductive atomic force microscopy (C-AFM and PC-AFM). Obtained results show that grain boundaries exhibit higher photocurrent than flat regions of the top perovskite layer, which indicates that excitons preferentially separate at the edges of the perovskite crystals i.e. at the grain boundaries. The study of the photoelectric mechanism at the nanoscale provides essential insights for the fabrication of high-performance perovskitebased photodetectors, where the device performance could potentially be fine tuned through grain boundary engineering. The demonstrated self-powered photodetector are promising for numerous applications in low-energy consumption optoelectronic devices.

Lead trihalide perovskites have been integrated with atomically thin WS2 and served as absorption layers to improve photoresponsivity in photodetectors. The combination of perovskites and two-dimensional (2D) transition-metal dichalcogenide (TMDC) materials provides the platform to study light–matter interactions and charge transfer mechanisms in optoelectronic devices. Herein, conductive and photoconductive atomic force microscopy were used to image the dark current and photocurrent generated in WS2/CH3NH3PbI3 (MAPbI3) heterostructures. Dark current measurement in the applied voltage range displays characteristic diode behavior, which can be well described by thermionic emission theory. Under laser illumination at 532 nm, the spatially resolved photocurrent images exhibit location-dependent photoresponse, where the photocurrent increases remarkably for the WS2/MAPbI3 heterostructures compared with the bare MAPbI3 regions. Furthermore, comparative surface roughness and 2D Fourier analysis of the topographic and current maps reveal that the interfacial conditions of the WS2/MAPbI3 heterojunctions play an important role in the charge separation process. In addition, WS2/MAPbI3-based photodetectors have been fabricated. Our study provides direct evidence that atomically thin TMDC monolayers can effectively assist the charge separation process and improve the light-to-electric energy conversion, which aids in the design principles and understanding of 2D heterostructured optoelectronic devices.