You Liu,Fang Liu,Jungan Wang,Hongyan Huang,Suhao Yan,Song Gao,Lin Wang,Wei Huang,Tianshi Qin
Wide-bandgap photovoltaics (WBPV) could not only provide electrical energy by photoelectronic conversion of the invisible part of the solar spectrum, but also usually had the unique advantage of high open circuit voltage ( V oc). In this work, we reported a novel HTM based on tetrakis (N-phenothiazine) Spirobifluorene (Spiro-PT), its HOMO energy level could be well matched with MAPbBr 3 perovskite HOMO energy level. This HTM could effectively suppress nonradiative recombination, which leads to an increase in the photovoltage of WBPV to more than 1.41 V. As a result, the n-i-p mesoscopic structured WBPV achieved a champion PCE of 7.36% as well as excellent operational stability exhibiting 91% of initial efficiency after 500 h continuous illumination without encapsulation. Based on the high V oc of the MAPbBr 3 /Spiro-PT device, the photovoltaic electrochromic device showed a response speed (the average coloring time was 40 s and the bleaching time was 272 s) and high average visible light transmittance contrast (about 37% in 450–780 nm), the corresponding electrochromic device with maximum dynamic contrast up to 46% at 600 nm between bleached and colored states. This WBPV-powered electrochromic system could provide a pathway towards stand-alone smart window technique for future energy-saving buildings.
Daocheng Hong,Jun Li,Sushu Wan,Ivan G. Scheblykin,Yuxi Tian
Photoluminescence (PL) of CH3NH3PbI3 perovskites depends strongly on sample preparation, atmosphere, crystal size, and so forth. However, the origin of these dependencies is always misunderstood because of the co-works of many different factors. Herein, we prepared hexagonal-shaped single crystals with tens of micrometers in size and observed a red-shifted PL emission (800–830 nm) mainly from the crystal edges besides the usual band-to-band transition (760 nm) from the central regions. Also, significantly different time-resolved dynamics and excitation power dependencies were observed. To summarize, we conclude that the red-shifted component comes from the depth of the crystal, where monomolecular recombination occurs involving photogenerated charges and unintentional doped charges, while the normal PL is emitted by bimolecular recombination from the surface layers. These results showed the significance of pure optical effects in perovskite crystals and would promote detailed understanding of the charge dynamics and recombination in perovskite crystalline materials of different geometries and sizes.
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