Passivation of electronic defects on the surface and at grain boundaries (GBs) of perovskite films has become one of the most effective tactics to suppress charge recombination in perovskite solar cells. It is demonstrated that trap states can be effectively passivated by Lewis acid or base functional groups. In this work, nicotinamide (NTM, commonly known as vitamin B3 or vitamin PP) serving as a Lewis base additive is introduced into the PbI2 and/or FAI: MABr: MACl precursor solution to obtain NTM modified perovskite films. It has been found that the NTM in the perovskite film can well passivate surface and GBs defects, control the film morphology and enhance the crystallinity via its interaction with a lone pair of electrons in nitrogen. In the presence of the NTM additive, we obtained enlarged perovskite crystal grain about 3.6 μm and a champion planar perovskite solar cell with efficiency of 21.72% and negligible hysteresis. Our findings provide an effective route for crystal growth and defect passivation to bring further increases on both efficiency and stability of perovskite solar cells.

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Cesium (Cs) contained triple-cation and mixed halide perovskite (CsFAMA) is broadly employed as light absorption layers for efficient and stable perovskite solar cells (PSCs) fabrication with high reproducibility. On the other hand, thermal annealing is a universal posttreatment method for perovskite films preparation. Moreover, thermal management highly depends on perovskite materials. However, no specialized study has been reported on CsFAMA perovskite to date. Herein, we have systematically investigated the influence of thermal annealing and annealing time on CsFAMA films and their solar cells. We demonstrated that heating time of 45 or 60 min at 100 °C is desirable. More interestingly, we found that the unannealed CsFAMA films exhibit ultrahigh photoluminescence (PL) intensities, much stronger than that of annealed films. Note that PL intensities gradually weaken as a function of annealing time. In particular, the PL intensities of fresh films (after antisolvent dripping) are at least 200 times higher than that of 60 min annealed films. To our knowledge, it is the first time to report this PL behavior. We speculate that it is due to quantum confinement effect of perovskite crystal nuclei and "cage effect" of DMSO intermediates in the fresh films. To this point, the unannealed CsFAMA films may have great potential in PL emission applications.

Microcrystalline silicon carbide (μc-SiC) films were prepared using hot wire chemical vapor deposition at low substrate temperature. The μc-SiC films were employed as window layers in microcrystalline silicon (μc-Si:H) n-i-p solar cells. Quantum efficiency (QE) and short circuit current density (JSC) in these n-side illuminated n-i-p cells were significantly higher than in standard p-i-n cells. A high QE current density of 26.7mA∕cm2 was achieved in an absorber layer thickness of 2μm. The enhanced JSC was attributed to the wide band gap of the μc-SiC layer and a sufficiently high hole drift mobility in μc-Si:H absorber layer.

A simple and low-cost method is suggested to fabricate nanochannels via Near-Field Electrospinning (NFES). In this process, orderly and patterned nanofibers direct-written by NFES are used as sacrificial templates. Well-defined nanochannels are available after the removal process of both sacrificial fibers and material coating over the fibers. The sacrificial fiber, controlled by NFES, dominates the channel geometry. The channel width ranges from 133 nm to 13.54 mu m while the applied voltage increases from 1.2 kV to 2.5 kV. Complicated wave-shape and grid pattern channels are presented under a corresponding movement of substrate. This method integrates electrospinning with conventional MEMS fabrication technology and has a potential in micro/nano manufacturing.National Natural Science Foundation of China [51035002, 51105320]; Fundamental Research Funds for the Central Universities [2010121039

Post-treatment of perovskite films plays a crucial role in obtaining high-performance perovskite solar cells (PSCs). Solvent annealing (SA), as a universal post-treatment strategy, is profoundly beneficial for enhancing the quality of perovskite films. Here, a mixed-solvent vapor (MSA)-assisted gradient thermal annealing strategy is developed for the post-treatment of perovskite films. It is found that the synergistic effect of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is significant for obtaining high-quality perovskite films with large grain size and low trap state density, which shows much better effects in comparison with single-solvent annealing. MSA-treated planar PSCs with a regular n–i–p structure achieve a maximum power conversion efficiency (PCE) of 19.76% with an average PCE of 19.29% under a reverse scan at a rate of 0.1 V/s, compared with an average PCE of 15.85% of the counterparts (TTA) with thermal annealing only. Such facile, effective, and low-cost annealing strategy exhibits commendable utilization potentiality to obtain high-quality perovskite films and efficient PSCs.