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It is essential to release annealing induced strain during the crystallization process to realize efficient and stable perovskite solar cells (PSCs), which does not seem achievable using the conventional annealing process. Here we report a novel and facile thermal gradient assisted crystallization strategy by simply introducing a slant angle between the preheated hot plate and the substrate. A distinct crystallization sequence resulted along the in-plane direction pointing from the hot side to the cool side, which effectively reduced the crystallization rate, controlled the perovskite grain growth, and released the in-plane tensile strain. Moreover, this strategy enabled uniform strain distribution in the vertical direction and assisted in reducing the defects and aligning the energy bands. The corresponding device demonstrated champion power conversion efficiencies (PCEs) of 23.70% and 21.04% on the rigid and flexible substrates, respectively. These highly stable rigid devices retained 97% of the initial PCE after 1097 h of storage and more than 80% of the initial PCE after 1000 h of continuous operation at the maximum power point. This novel strategy opens a simple and effective avenue to improve the quality of perovskite films and photovoltaic devices via strain modulation and defect passivation.

Organic-inorganic hybrid semiconducting (OIHS) materials, which can detect broader spectral regions, are highly desired in several applications including biomedical imaging, night vision, and optical communications. Although lead (Pb)-halide perovskites have reached a mature research stage, high toxicity of Pb hinders their large-scale viability. Tin (Sn)-based perovskites are the most common OIHS broadband light absorbers that replace toxic Pb; however, they are extremely unstable due to the notorious Sn

A deficiency in the photoelectrical dynamics at the interface due to the surface traps of the TiO2 electron transport layer (ETL) has been the critical factor for the inferiority of the power conversion efficiency (PCE) in the perovskite solar cells. Despite its excellent energy level alignment with most perovskite materials, its large density of surface defect as a result of sub lattice vacancies has been the critical hurdle for an efficient photovoltaic process in the device. Here, we report that atoms thick 2D TiS2 layer grown on the surface of a (001) faceted and single-crystalline TiO2 nanograss (NG) ETL have effectively passivated the defects, boosting the charge extractability, carrier mobility, external quantum efficiency, and the device stability. These properties allow the perovskite solar cells (PSCs) to produce a PCE as high as 18.73% with short-circuit current density (Jsc), open-circuit voltage (Voc), and fill-factor (FF) values as high as 22.04 mA/cm2, 1.13 V, and 0.752, respectively, a 3.3% improvement from the pristine TiO2-NG-based PSCs. The present approach should find an extensive application for controlling the photoelectrical dynamic deficiency in perovskite solar cells.

Surface litter layer strongly influences CO2, N2O, and CH4 fluxes (FCO2, FN2O, and FCH4) between the atmosphere and forest floor through litter decomposition (litter-internal, fL-L) or interactions between litter and mineral soil (litter-induced, fL-S). However, the relative contribution of fL-L or fL-S to these greenhouse gas (GHG) fluxes in forests at different succession stages remain unclear. We conducted a field experiment where surface litter was either removed (LR), left intact (CT), doubled (LD), or exchanged (LE) in a Masson pine forest (PF, early stage of succession) and an evergreen broadleaved forest (BF, climax of succession) at the Dinghushan Nature Reserve in southern China, and studied the responses of FCO2, FN2O, and FCH4 from August 2012 to July 2013. The results showed that both FCO2 and FN2O were increased by LD treatment with a greater increase in BF (41% for FCO2 and 30% for FN2O) and decreased by LR treatment with the greater decrease in PF (−61% for FCO2 and −58% for FN2O). LD treatment decreased FCH4 by 14% in PF and 6% in BF, and LR treatment increased FCH4 by 5% in PF and 18% in BF. fL-S contributed more to FCO2 (36%) and FN2O (45%) than fL-L in PF, whereas contributions of fL-L to FCO2 (41%) and FN2O (30%) were much bigger than fL-S in BF. The greater FCH4 in PF and BF resulted from the contributions of fL-L (−14%) and fL-S (−12%), respectively. Our results indicated that fL-L is the major source of GHG fluxes in BF, whereas fL-S dominates GHG fluxes in PF. The results provide a scientific reference for quantifying the contributions of fL-L and fL-S to GHG fluxes during the subtropical forest succession and should be considered in ecosystem models to predict global warming in the future.

The efficient electron transfer at the interface of the electron transport layer (ETL) and perovskite, and the transportation along the ETL and collection at the electrode are characteristics that are critically governed by the properties of the ETL. Both characteristics are fundamental for the fabrication of high-performance perovskite solar cells (PSC). So far, mesoporous TiO2 might be considered a versatile ETL as its structure can provide an enormous heterojunction with the perovskite absorber. However, its inert (101) pore facet, massive dead-end pore structure, and extensive grain boundary with the underlying layers in the PSC device have made them unlikely to meet those basic criteria. Here, we have come up with a new design of TiO2 ETL that provides a high carrier dynamic in the device. It is a 3 nm thick high-energy (001) faceted single-crystalline nanograss-like structure (TNG) that is vertically grown on the ITO surface. With these unique structural properties, we achieved an enhanced carrier extraction from the perovskite layer, transportation along the ETL and collection at the electrode. Our results indicate that the charge-transfer dynamic at the TNG–perovskite interface and transport in the device are up to more than 2 times faster than those in the control device or in the recently reported results. With this property, we recorded a power conversion efficiency (PCE) as high as 21.60% (or at the level of 20.84% on average) from the TNG-based PSC with the device area as high as ∼0.17 cm2 using triple cation Cs0.05[MA0.13FA0.87]0.95Pb(I0.87Br0.13)3 perovskites, an improvement as high as 18% from the control device. The TNG with its unique structure and surface chemistry may become a potential platform for the fabrication of a high-performance PSC device via combination with a high-performance perovskite system.

Two-dimensional (2D) perovskite materials are a promising platform to construct high performance photodetectors due to their novel structure, high stability, resistance to ion migration and decent light harvesting ability. However, the detection range of 2D perovskite photodetectors is limited due to their large bandgap. Here, self-trapped states with a lower bandgap were created by introducing Sn into a 2D perovskite ((C6H5C2H4NH3)2PbI4, (PEA)2PbI4). Although previously the excitons in the self-trapped states have been regarded as localized excitons, an obvious photocurrent generated by the dissociation of excitons in self-trapped states has been observed. With this property, the detection range of 2D perovskite photodetectors has been successfully extended. Additionally, the special 2D structure of (PEA)2PbI4 endows the device with high stability and great resistance for ion migration to endure long-term (over 1000 s) consistent work without degradation in performance. This facile doping method for extending the detection range of 2D perovskite photodetectors will greatly broaden their application potential.

Realization of remote wearable health monitoring (RWHM) technology for the flexible photodiodes is highly desirable in remote-sensing healthcare systems used in space stations, oceans, and forecasting warning, which demands high external quantum efficiency (EQE) and detectivity in NIR region. Traditional inorganic photodetectors (PDs) are mechanically rigid and expensive while the widely reported solution-processed mixed tin-lead (MSP) perovskite photodetectors (PPDs) exhibit a trade-off between EQE and detectivity in the NIR region. Herein, a novel functional passivating antioxidant (FPA) strategy has been introduced for the first time to simultaneously improve crystallization, restrain Sn

A deficiency in the photoelectrical dynamics at the interface due to the surface traps of the TiO