Migration of ions can lead to photoinduced phase separation, degradation, and current-voltage hysteresis in perovskite solar cells (PSCs), and has become a serious drawback for the organic-inorganic hybrid perovskite materials (OIPs). Here, the inhibition of ion migration is realized by the supramolecular cation-π interaction between aromatic rubrene and organic cations in OIPs. The energy of the cation-π interaction between rubrene and perovskite is found to be as strong as 1.5 eV, which is enough to immobilize the organic cations in OIPs; this will thus will lead to the obvious reduction of defects in perovskite films and outstanding stability in devices. By employing the cation-immobilized OIPs to fabricate perovskite solar cells (PSCs), a champion efficiency of 20.86% and certified efficiency of 20.80% with negligible hysteresis are acquired. In addition, the long-term stability of cation-immobilized PSCs is improved definitely (98% of the initial efficiency after 720 h operation), which is assigned to the inhibition of ionic diffusions in cation-immobilized OIPs. This cation-π interaction between cations and the supramolecular π system enhances the stability and the performance of PSCs efficiently and would be a potential universal approach to get the more stable perovskite devices.

Toxicity and chemical instability issues of halide perovskites based on organic-inorganic lead-containing materials still remain as the main drawbacks for perovskite solar cells (PSCs). Herein, we discuss the preparation of copper (Cu)-based hybrid materials, where we replace lead (Pb) with nontoxic Cu metal for lead-free PSCs, and investigate their potential toward solar cell applications based on experimental and theoretical studies. The formation of (CHNH)CuX [(CHNH)CuCl, (CHNH)CuClI, and (CHNH)CuClBr] was discussed in details. Furthermore, it was found that chlorine (Cl) in the structure is critical for the stabilization of the formed compounds. Cu-based perovskite-like materials showed attractive absorbance features extended to the near-infrared range, with appropriate band gaps. Green photoluminescence of these materials was obtained because of Cu ions. The power conversion efficiency was measured experimentally and estimated theoretically for different architectures of solar cell devices.

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INTRODUCTIONThe aim of this review was to systemically analyse trials evaluating the efficacy of routine on-table cholangiography (R-OTC) versus no on-table cholangiography (N-OTC) in patients undergoing cholecystectomy.METHODSRandomised trials evaluating R-OTC versus N-OTC in patients undergoing cholecystectomy were selected and analysed.RESULTSFour trials (1 randomised controlled trial on open cholecystectomy and 3 on laparoscopic cholecystectomy) encompassing 860 patients undergoing cholecystectomy with and without R-OTC were retrieved. There were 427 patients in the R-OTC group and 433 patients in the N-OTC group. There was no significant heterogeneity among trials. Therefore, in the fixed effects model, N-OTC did not increase the risk (p=0.53) of common bile duct (CBD) injury, and it was associated with shorter operative time (p<0.00001) and fewer peri-operative complications (p<0.04). R-OTC was superior in terms of peri-operative CBD stone detection (p<0.006) and it reduced readmission (p<0.03) for retained CBD stones.CONCLUSIONSN-OTC is associated with shorter operative time and fewer peri-operative complications, and it is comparable to R-OTC in terms of CBD injury risk during cholecystectomy. R-OTC is helpful for peri-operative CBD stone detection and there is therefore reduced readmission for retained CBD stones. The N-OTC approach may be adopted routinely for patients undergoing laparoscopic cholecystectomy providing there are no clinical, biochemical or radiological features suggestive of CBD stones. However, a major multicentre randomised controlled trial is required to validate this conclusion.

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