Hybrid perovskites have rapidly emerged as highly promising optoelectronic materials for perovskite solar cells (PSCs), whereas solution‐processed perovskite films usually contain a large amount of grain‐boundary network, which is unbeneficial for efficient film function, including charge transport and environmental stability. Herein, a liquid crystal (LC) molecule is first used as a “binding agent” to connect grains and fill grain boundaries of perovskite. The LC molecule (4′‐heptyl‐4‐biphenylcarbonitrile) interacts with PbI2 to control the crystal orientation for fine and oriented perovskite grains, which accelerates electron transport and enhances environmental stability. Consequently, compared with the pristine devices, the power conversion efficiency of the LC‐based device increases from 17.14% to 20.19% with a high fill factor (over 80%). Remarkably, the LC‐based PSCs retain 92% of their initial efficiency at 25 °C, and a relative humidity of 70% after 500 h, whereas the control samples are almost degraded completely under the same conditions.
Existing experiments have revealed that methylammonium lead iodide (MAPbI 3 or CH 3 NH 3 PbI 3 ) materials show favorable gas-sensing properties to reducing gas NH 3 and oxidizing gases O 2 and O 3 . The first step to effective gas-sensing by using semiconductor materials for gas-sensing applications is to recognize a target gas through gas-solid interaction. To explore the sensing mechanisms of perovskite materials to different oxidizing and reducing gases, the changes of skeleton structures of MAPbI 3 in reducing gas NH 3 and oxidizing gases O 2 and O 3 , adsorption energy, and charge transfer between gases and semiconductors are investigated through large-scale quantum dynamics simulations. By using three adsorption models, the differences and similarities of adsorption mechanisms of MAPbI 3 for gases NH 3 , O 2 , and O 3 are illustrated. These adsorption mechanisms are expected to provide new ideas for developing innovative sensing elements made of perovskite materials with stronger stability, high sensitivity, and high selectivity.
In article no. http://doi.wiley.com/10.1002/solr.1900125, Guokun Ma, Hao Wang, and co‐workers use liquid crystal (LC) molecule (4'‐heptyl‐4‐biphenylcarbonitrile) as a binding agent to connect the grain boundaries of perovskites. After treatment with the LC, perovskite crystal growth orientation can be controlled and the electron transport process is accelerated. Remarkably, the LC greatly contributes to the environmental stability of the devices.
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