Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most widely used hole transport materials for perovskite solar cells (PVSCs) with a p‐i‐n structure. However, the solar cells based on PEDOT:PSS show a low photoconversion efficiency due to the poor crystallinity of a perovskite film on it. Besides, the acidity of PEDOT:PSS performance critically influences the long‐term stability of PVSCs. Herein, a layer of the discrete SnO 2 nanoparticle film is deposited on the surface of PEDOT:PSS to modify the surface of the PEDOT:PSS film. This discrete SnO 2 nanoparticle film acts as the buffer layer between the PEDOT:PSS and MAPbI 3 , which not only improves the crystallization of the quality of the perovskite film, but also provides a selective‐carrier pathway to enhance the extraction of holes and to block the diffusion of electrons. The SnO 2 modified devices show a power conversion efficiency of 18.04%, with a great improvement compared with the 12.24% efficiency of PEDOT:PSS only devices. This work demonstrates that it is possible to enhance the performance of PVSCs via n‐type nanoparticle modification of hole transport layer and provides a new guidance for PVSCs interface modification engineering.
Researchers have been working to develop stable and convenient test strips for detecting heavy metals. This paper reports a new portable lead ion test strip based on the exceptional photoluminescence properties of CsPbBr3. The CsBr films deposited on different substrates (rigid, semi-rigid, and flexible substrates) display highly selective luminescent response to Pb2+. For the flexible substrate, CsBr fluorescent probe not only shows lightweight, easy to use in large-scale manufacturing but also exhibits long detection lifetime. In comparison to organometallic perovskite fluorescence sensing of Pb2+, the CsBr fluorescent probe displays better stability and higher detection limit. Moreover, the used test strip can be reused to detect Cl- in solution, the CsBr fluorescent probe also shows a potential for multi-testing in recycling applications.
Fabrication of nanowires in polymer films can dramatically enhance the mobility of thin‐film transistors (TFTs). Unlike the popular method of forming nanowires after spin‐coating films, here a water‐bath method to fabricate the micrometer‐long nanowires in the poly(3‐hexylthiophene) (P3HT) solution is introduced, which is suitable for large‐area printing electronic application. The resulting transistor exhibits significantly enhanced mobility and excellent device stability. However, the threshold voltage of the device is increased, compared with the amorphous film device. The underlying mechanism of the mesoscale crystalline induced threshold voltage increase has been rarely studied. The temperature‐dependent characteristics imply that the activation energy of the device with nanowires is higher than that of the amorphous one, indicating nanowires can introduce deep traps. This suggests that the charge transport is mainly limited by the deep traps at the junctions between the nanowires considering the trap density inside the nanowires is significantly low. The deep traps introduced by the junctions can increase the threshold voltage as the device needs higher voltage to fill these traps in the channel before the device is turned on. This explains why the devices with nanowires have an increased threshold voltage while their mobilities are dramatically enhanced.
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