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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.

Organic–inorganic hybrid perovskites have emerged as promising functional materials for high‐performance photodetectors. However, the toxicity of Pb and the lack of internal gain mechanism in typical perovskites significantly hinder their practical applications. Herein, a low‐voltage and high‐performance photodetector based on a single layer of lead‐free Sn‐based perovskite film is reported. The device shows broadband response from ultraviolet to near‐infrared light with a responsivity up to 105 A W−1 and a high gain at a low operating voltage. The outstanding performance is attributed to the high hole mobility, p‐doping nature, and excellent optoelectronic properties of the Sn‐based perovskite. Moreover, the device is assembled on a flexible substrate and demonstrates both high sensitivity and good bending stability. This work demonstrates a route for realizing nontoxic, low‐cost, and high‐performance perovskite photodetectors with a simple device structure.

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.

Semitransparent solar cells can provide not only efficient power-generation but also appealing images and show promising applications in building integrated photovoltaics, wearable electronics, photovoltaic vehicles and so forth in the future. Such devices have been successfully realized by incorporating transparent electrodes in new generation low-cost solar cells, including organic solar cells (OSCs), dye-sensitized solar cells (DSCs) and organometal halide perovskite solar cells (PSCs). In this review, the advances in the preparation of semitransparent OSCs, DSCs, and PSCs are summarized, focusing on the top transparent electrode materials and device designs, which are all crucial to the performance of these devices. Techniques for optimizing the efficiency, color and transparency of the devices are addressed in detail. Finally, a summary of the research field and an outlook into the future development in this area are provided.

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 MAPbI3 perovskite films on MoS2 flakes is reported. Under transmission electron microscopy, in-plane coupling between the perovskite and the MoS2 crystal lattices is observed, leading to perovskite films with larger grain size, lower trap density, and preferential growth orientation along (110) normal to the MoS2 surface. In perovskite solar cells, when perovskite active layers are grown on MoS2 flakes coated on hole-transport layers, the power conversion efficiency is substantially enhanced for 15%, relatively, due to the increased crystallinity of the perovskite layer and the improved hole extraction and transfer rate at the interface. This work paves a way for preparing high-performance perovskite solar cells and other optoelectronic devices by introducing 2D materials as interfacial layers.