Improving the quality of perovskite poly‐crystalline film is essential for the performance of associated solar cells approaching their theoretical limit efficiency. Pinholes, unwanted defects, and nonperovskite phase can be easily generated during film formation, hampering device performance and stability. Here, a simple method is introduced to prepare perovskite film with excellent optoelectronic property by using acetic acid (Ac) as an antisolvent to control perovskite crystallization. Results from a variety of characterizations suggest that the small amount of Ac not only reduces the perovskite film roughness and residual PbI2 but also generates a passivation effect from the electron‐rich carbonyl group (CO) in Ac. The best devices produce a PCE of 22.0% for Cs0.05FA0.80MA0.15Pb(I0.85Br0.15)3 and 23.0% for Cs0.05FA0.90MA0.05Pb(I0.95Br0.05)3 on 0.159 cm2 with negligible hysteresis. This further improves device stability producing a cell that maintained 96% of its initial efficiency after 2400 h storage in ambient environment (with controlled relative humidity (RH) <30%) without any encapsulation.

UV-induced degradation and parasitic ultraviolet (UV) absorption by the “sun-facing” carrier transport layer in a perovskite cell hinders stability and electrical performance when the perovskite cell is a top cell for a Si-based tandem. In this work, we tackle these issues by applying textured polydimethylsiloxane (PDMS) films that incorporate a down-shifting material (Ba,Sr)2SiO4:Eu2+ micron phosphor on the front of monolithic perovskite/silicon tandem cells. This film serves multiple purposes: antireflective control for the top cell, light trapping in the Si cell, as well as absorbing UV and re-emitting green light with high quantum yield. When applied onto a 4 cm2 monolithic perovskite/silicon tandem solar cell, the power conversion efficiency was improved from 20.1% (baseline device without any antireflective film) to 22.3% (device with an antireflective film but without the phosphors) and to 23.1% (device with down-shifting phosphor-incorprated antireflective film). The steady-state efficiency of 23.0% and a high fill factor (FF) of 81% achieved by the champion device are the highest values to date for a monolithic perovskite/silicon tandem that uses a homojunction silicon bottom cell. Moreover, results of a continuous UV irradiation test show that this composite down-shifting antireflection film significantly enhances the UV stability for the tandem device. This work demonstrates an elegant approach for improving the efficiency and stability for larger-area perovskite/silicon tandems.

Three iridium(III)-based metal-organic frameworks (MOFs), namely [Cd{Ir(ppy-COO)}(DMF)(HO)]·6HO·2DMF (1), [Cd{Ir(ppy-COO)}(DMA)(HO)]·0.5HO·2DMA (2), and [Cd{Ir(ppy-COO)}(DEF)(HO)]·8HO·2DEF (3) (ppy-COOH = methyl-3-(pyridin-2-yl)benzoic acid, DMF = N,N-dimethylformamide, DMA = N,N-dimethylacetamide, DEF = N,N-diethylformamide), have been synthesized and characterized. Single-crystal structural determinations reveal that compounds 1-3 are isostructural, showing a three-dimensional framework structure with (3,6) connected rtl topologyin whose trimers of {Cd(COO)} are cross-linked by Ir(ppy-COO). The structures are completely different from those of other Ir(III)-based MOFs. Compound 1 was selected for a detailed study on sensing properties. The excellent luminescence as well as good water stability of 1 makes it a highly selective and sensitive multiresponsive luminescent sensor for Fe and CrO. The detection limits are 67.8 and 145.1 ppb, respectively. Compound 1 can also be used as an optical sensor for selective sensing of adenosine triphosphate (ATP) over adenosine diphosphate (ADP) and adenosine monophosphate (AMP) in aqueous solution. This is the first example of iridium(III)-based MOFs for the optical detection of Fe, CrO, and ATP. More interestingly, the luminescent composite film doped with 1% (w/w) of compound 1, 1@PMMA (PMMA = poly(methyl methacrylate)), can be successfully prepared, which endows efficient sensitivity for Fe and CrO detection and thus provides great potential for future applications.