As the black cesium lead iodide (CsPbI3) tends to transit into a yellow δ-phase at ambient, it is imperative to develop a stabilized black phase for photovoltaic applications. Herein, we report a distorted black CsPbI3 film by exploiting the synergistic effect of hydroiodic acid (HI) and phenylethylammonium iodide (PEAI) additives. It is found that the HI induces formation of hydrogen lead iodide (HPbI3+x), an intermediate to the distorted black phase with appropriate band gap of 1.69 eV; while PEAI provides nucleation for optimized crystallization. More importantly, it stabilizes the distorted black phase by hindering phase transition via its steric effects. Upon optimization, we have attained solar cell efficiency as high as 15.07%. Specifically, the bare cell without any encapsulation shows negligible efficiency loss after 300 h of light soaking. The device keeps 92% of its initial cell efficiency after being stored for 2 months under ambient conditions.

Quantum efficiencies of organic-inorganic hybrid lead halide perovskite light-emitting devices (LEDs) have increased significantly, but poor device operational stability still impedes their further development and application. All-inorganic perovskites show better stability than the hybrid counterparts, but the performance of their respective films used in LEDs is limited by the large perovskite grain sizes, which lowers the radiative recombination probability and results in grain boundary related trap states. We realize smooth and pinhole-free, small-grained inorganic perovskite films with improved photoluminescence quantum yield by introducing trifluoroacetate anions to effectively passivate surface defects and control the crystal growth. As a result, efficient green LEDs based on inorganic perovskite films achieve a high current efficiency of 32.0 cd A−1 corresponding to an external quantum efficiency of 10.5%. More importantly, our all-inorganic perovskite LEDs demonstrate a record operational lifetime, with a half-lifetime of over 250 h at an initial luminance of 100 cd m−2.

It is imperative to develop a large-aspect-ratio grainbased thin film with low trap density for high-performance inorganic perovskite CsPbI 2 Br solar cells. Herein, by using Mn 2+ ion doping to modulate film growth, we achieved CsPbI 2 Br grains with aspect ratios as high as 8. It is found that Mn 2+ ions insert into the interstices of the CsPbI 2 Br lattice during the growth process, leading to suppressed nucleation and a decreased growth rate. The combination aids in the achievement of larger CsPbI 2 Br crystalline grains for increased J SC values as high as 14.37 mA/cm 2 and FFs as large as 80.0%. Moreover, excess Mn 2+ ions passivate the grain boundary and surface defects, resulting in effectively decreased recombination loss with improved hole extraction efficiency, which enhances the built-in electric field and hence increases V OC to 1.172 V. As a result, the champion device achieves stabilized efficiency as high as 13.47%, improved by 13% compared with only 11.88% for the reference device.

Quasi-two-dimensional (quasi-2D) Ruddlesden–Popper (RP) perovskites such as BA2Csn–1PbnBr3n+1 (BA = butylammonium, n > 1) are promising emitters, but their electroluminescence performance is limited by a severe non-radiative recombination during the energy transfer process. Here, we make use of methanesulfonate (MeS) that can interact with the spacer BA cations via strong hydrogen bonding interaction to reconstruct the quasi-2D perovskite structure, which increases the energy acceptor-to-donor ratio and enhances the energy transfer in perovskite films, thus improving the light emission efficiency. MeS additives also lower the defect density in RP perovskites, which is due to the elimination of uncoordinated Pb2+ by the electron-rich Lewis base MeS and the weakened adsorbate blocking effect. As a result, green light-emitting diodes fabricated using these quasi-2D RP perovskite films reach current efficiency of 63 cd A−1 and 20.5% external quantum efficiency, which are the best reported performance for devices based on quasi-2D perovskites so far.

Here, a high-performance graded bandgap structure-based solar cell was designed and demonstrated, comprising a CsPbI 2 Br bottom cell and a CsPbI 3 QD top cell. Several optimizations were conducted to boost the device performance. As a result, the extended photoresponse, high carrier mobility, and well-matched energy levels afford a record power conversion efficiency of 14.45%, coupled with a high J SC of 15.25 mA/cm 2 . The result shows that optical and energy-band manipulation is an effective approach for improving the performance of inorganic perovskite solar cells.