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Cesium‐based all‐inorganic wide‐bandgap perovskite solar cells (AIWPSCs) have been demonstrated with exceptional optoelectronic properties such as intrinsic optical wide‐bandgap and high thermal stability, which make them suitable candidates for the front sub‐cells of tandem solar cells (TSCs). Passivation of perovskite surface and interface is a matter of common interest in this community since all‐inorganic perovskites always suffer from non‐ideal crystallization such as phase impurity, high defect density, and non‐uniform morphology. Despite these shortcomings, numerous efforts have been devoted in recent years to pursuing high‐performance AIWPSCs, which exhibit an abruptly increased power conversion efficiency (PCE) from 2.9% to over 21.0%. In view of not having a thorough summary about the advancements on AIWPSCs, herein, a comprehensive review is given to highlight the recent device performance progress of AIWPSC, particularly focusing on the strategies to passivate the defects of all‐inorganic perovskite, namely, additive engineering, solvent engineering, interface modification, and the exploration of new charge transport materials (CTMs) for improving the phase stability and PCE of AIWPSCs. Finally, a conclusive outlook on AIWPSCs will be given to provide our perspectives aiming to inspire the further development of AIWPSCs. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes in tandem structures (TOLEDs) have long been an effective strategy to realize multifold increased electroluminescence (EL) efficiency relative to the single‐unit OLEDs, making TOLEDs promising candidates for lighting and display applications. Benefitted from the development of organic emitters, hybrid tandem OLEDs (HTOLEDs) composing two or more types of OLED emitters (phosphorescence, fluorescence, and thermally‐activated delayed fluorescence (TADF)) are developed. The different energy conversion processes of these emitters can facilitate manipulated exciton distribution inside the device, leading to enhanced device performance. On the other hand, different emission technologies can also be integrated to form another kind of hybrid tandem light‐emitting diodes (HTLED) thanks to the compatibility of OLEDs with quantum dot LEDs (QLEDs) and perovskite LEDs (PeLEDs). In this review, the performance of different types of HTOLEDs and HTLEDs is comprehensively reviewed particularly focusing on the exciton regulations and manipulation of emission spectra in the sub‐units, aiming to provide guidelines for the EL performance optimization of HTOLEDs. [ABSTRACT FROM AUTHOR]

Perovskite light-emitting diodes (PeLEDs) have been attracting widespread attention owing to their unique advantages such as high luminance, narrow emission spectra and high color purity. However, the solution-processed fabrication method makes the deposition of multi-emitting layers of perovskite films for white PeLEDs challenging. Moreover, modulating the emission color by adjusting the thickness of the emitting layers will result in reduced optoelectronic performance of the polycrystalline perovskite films. Therefore, strategies for achieving high-performance white PeLEDs are urgently needed. This study developed a newly designed perovskite/organic hybrid tandem light-emitting diode (POTLED) by combining a bottom PeLED unit with a top organic light-emitting diode (OLED) unit. The vacuum deposition process of the OLED avoids damaging the underlying PeLED unit. Additionally, the emission color of the tandem device can be tuned by adjusting the thickness of the organic emitting layer while maintaining the optoelectronic properties of the perovskite layer. As a result, a high-efficiency green POTLED with an outstanding current efficiency of 144.2 cd A−1, an external quantum efficiency of 41.1%, and a luminance of over 32 000 cd m−2 is achieved, illustrating the feasibility and potential of the hybrid tandem perovskite-organic structure to realize high-efficiency white-color perovskite-based devices. [ABSTRACT FROM AUTHOR]

Controlling the crystallization to achieve high‐quality homogeneous perovskite film is the key strategy in developing perovskite electronic devices. Here, an in situ dynamic optical probing technique is demonstrated that can monitor the fast crystallization of perovskites and effectively minimize the influence of laser excitation during the measurement. This study finds that the typical static probing technique would damage and induce phase segregation in the perovskite films during the excitation. These issues can be effectively resolved with the dynamic probing approach. It also found that the crystallization between MAPbI3 and MAPbI2Br is strikingly different. In particular, MAPbI2Br suffers from inefficient nucleation during the spin‐coating that strongly affects the uniform crystal growth in the annealing process. The commonly used pre‐heating process is found at a lower temperature not only can further promote the nucleation but also to complete the crystallization of MAPbI2Br. The role of further annealing at a higher temperature is to facilitate ion‐dissociation on the crystal surface to form a passivation layer to stabilize the MAPbI2Br lattices. The device performance is strongly correlated with the film formation mechanism derived from the in situ results. This work demonstrates that the in situ technique can provide deep insight into the crystallization mechanism, and help to understand the growth mechanism of perovskites with different compositions and dimensionalities. [ABSTRACT FROM AUTHOR]

Passivation of organometal halide perovskites with polar molecules has been recently demonstrated to improve the photovoltaic device efficiency and stability. However, the mechanism is still elusive. Here, it is found that both polymers with large and small dipole moment of 3.7 D and 0.6 D have negligible defect passivation effect on the MAPbI3 perovskite films as evidenced by photothermal deflection spectroscopy. The photovoltaic devices with and without the polymer additives also have comparable power conversion efficiencies around 19%. However, devices with the additives have noticeable improvement in stability under continuous light irradiation. It is found that although the initial mobile ion concentrations are comparable in both devices with and without the additives, the additives can strongly suppress the ion migration during the device operation. This contributes to the significantly enhanced electrical‐field stress tolerance of the perovskite solar cells (PVSCs). The PVSCs with polymer additives can operate up to −2 V reverse voltage bias which is much larger than the breakdown voltage of −0.5 V that has been commonly observed. This study provides insight into the role of additives in perovskites and the corresponding device degradation mechanism. [ABSTRACT FROM AUTHOR]

Mixed-organic-cation FA1−xMAxPbI3 perovskites are currently attracting intensive attention for their high photovoltaic performance. However, FA1−xMAxPbI3 usually has an undesired non-perovskite phase leading to a compromised efficiency, and a facile strategy to achieve pure-phase FA1−xMAxPbI3 has been rarely reported. Here, we demonstrate a facile approach to form δ-phase free FA1−xMAxPbI3 using a non-stoichiometric precursor solution. It is found that a small amount of excess methylammonium iodide (MAI) added to the precursor solution has a profound effect on perovskite crystallization during the liquid-to-solid phase transformation. Using an in situ photoluminescence spectroscopy measurement, it is found that the excess MAI can promote the formation of FA1−xMAxPbI3 and facilitate the cation-exchange between organic FA+ and MA+ during the film formation. Based on the optimized pure-phase FA1−xMAxPbI3, the perovskite solar cells exhibit an encouraging power conversion efficiency (PCE) of 17.40%. This study demonstrates a facile method to achieve high performance FA dominating mixed-organic-cation perovskite devices while providing insight into the ion-exchange process during perovskite crystallization. [ABSTRACT FROM AUTHOR]