Tin‐based perovskites with excellent optoelectronic properties and suitable band gaps are promising candidates for the preparation of efficient lead‐free perovskite solar cells (PSCs). However, it is challenging to prepare highly stable and efficient tin‐based PSCs because Sn2+ in perovskites can be easily oxidized to Sn4+ upon air exposure. Here we report the fabrication of air‐stable FASnI3 solar cells by introducing hydroxybenzene sulfonic acid or its salt as an antioxidant additive into the perovskite precursor solution along with excess SnCl2. The interaction between the sulfonate group and the Sn2+ ion enables the in situ encapsulation of the perovskite grains with a SnCl2–additive complex layer, which results in greatly enhanced oxidation stability of the perovskite film. The corresponding PSCs are able to maintain 80 % of the efficiency over 500 h upon air exposure without encapsulation, which is over ten times longer than the best result reported previously. Our results suggest a possible strategy for the future design of efficient and stable tin‐based PSCs.

Poor stability of organic–inorganic halide perovskite materials in humid condition has hindered the success of perovskite solar cells in real applications since controlled atmosphere is required for device fabrication and operation, and there is a lack of effective solutions to this problem until now. Here we report the use of lead (II) thiocyanate (Pb(SCN)2) precursor in preparing perovskite solar cells in ambient air. High-quality CH3NH3PbI3−x(SCN)x perovskite films can be readily prepared even when the relative humidity exceeds 70%. Under optimized processing conditions, we obtain devices with an average power conversion efficiency of 13.49% and the maximum efficiency over 15%. In comparison with typical CH3NH3PbI3-based devices, these solar cells without encapsulation show greatly improved stability in humid air, which is attributed to the incorporation of thiocyanate ions in the crystal lattice. The findings pave a way for realizing efficient and stable perovskite solar cells in ambient atmosphere.

Semitransparent perovskite solar cells are prepared by laminating graphene transparent electrodes on the top for the first time. The device performance is optimized by improving the conductivity of the graphene electrodes and the contact between the graphene and the perovskite active layers during the lamination process. The devices show high power conversion efficiencies when they are illuminated from both sides.

Organolead halide perovskites have emerged as the most promising materials for various optoelectronic devices, especially solar cells, because of their excellent optoelectronic properties. Here, we present the first report of low-voltage high-gain phototransistors based on perovskite/organic-semiconductor vertical heterojunctions, which show ultrahigh responsivities of ~109A W–1 and specific detectivities of ~1014 Jones in a broadband region from the ultraviolet to the near infrared. The high sensitivity of the devices is attributed to a pronounced photogating effect that is mainly due to the long carrier lifetimes and strong light absorption in the perovskite material. In addition, flexible perovskite photodetectors have been successfully prepared via a solution process and show high sensitivity as well as excellent flexibility and bending durability. The high performance and facile solution-based fabrication of the perovskite/organic-semiconductor phototransistors indicate their promise for potential application for ultrasensitive broadband photodetection.

non-wetting surface can enable the growth of perovskite films with large grain size and high crystallinity, which impressively suppresses the nonradiative recombination and improves the photovoltaic performance of PSCs. [23] Snaith and co-workers have used a self-assembled fullerene monolayer to grow high-quality perovskite films and passivate the defects on TiO 2 layers, leading to hysteresis-free PSCs with good photovoltaic performance. [25] Therefore, proper surface modification of substrates can decrease the density of nucleation sites and enlarge the grains of perovskite films. However, the orientation of the solution processed perovskite films cannot be conveniently controlled.Van der Waals (vdW) epitaxy is a prevalent technique for preparing high-quality semiconductor films with preferential orientations on 2D substrates with smooth and dangling-bond-free surfaces. [26][27][28] The weak vdW interactions between the crystals and the substrates can enable epitaxial growth of the films with high crystallographic orientation and low defect states even in the presence of large lattice mismatch and symmetry misfit between them. [29,30] Recently, Duan and co-workers realized scalable solution-phase vdW epitaxial growth of cubic PbSe layer on 2D rhombohedral Bi 2 Se 3 nanoplates. [31] Liu and co-workers also employed solution-phase vdW epitaxy strategy to fabricate ultrathin graphdiyne film with high quality by using 2D graphene as a growing template. [32] Inspired by the intriguing effects, we consider that dangling-bond-free 2D materials with proper lattice parameters can be utilized as growth templates for preparing high-quality perovskite films with a controllable orientation.Molybdenum disulfide (MoS 2 ) is a promising 2D material with high carrier mobilities and a suitable energy band structure for many optoelectronic applications. [33][34][35] Due to its dangling-bondfree and clean surface, MoS 2 has been used as growth templates for preparing vdW epitaxial 2D materials. [36] In this paper, solution processed large few-layer MoS 2 flakes have been employed as a growth template for perovskite films. We find for the first time the vdW epitaxial growth of MAPbI 3 perovskite on MoS 2 flakes, leading to highly oriented perovskite films with large grain sizes and low defect densities. Transmission electron micro scopy (TEM) images demonstrate that the (008) plane of MAPbI 3 and the (110) plane of MoS 2 can match perfectly, which facilities the out-of-plane growth of perovskite films with preferential orientation along (110). Then, MoS 2 flakes are modified on The quality of perovskite films is critical to the performance of perovskite solar cells. However, it is challenging to control the crystallinity and orientation of solution-processed perovskite films. Here, solution-phase van der Waals epitaxy growth of MAPbI 3 perovskite films on MoS 2 flakes is reported. Under transmission electron microscopy, in-plane coupling between the perovskite and the MoS 2 crystal lattices is observed, leading to perovskite films ...