Indium- and Platinum-Free Counter Electrode for Green Mesoscopic Photovoltaics through Graphene Electrode and Graphene Composite Catalysts: Interfacial Compatibility

The scarcity and noble indium and platinum (Pt) are important elements in photoelectric nanomaterials. Therefore, development of low cost alternative materials to meet different practical applications is an urgent need. Two-dimensional (2D) layered graphene (GE) with unique physical, mechanical, and electrical properties has recently drawn a great deal of attention in various optoelectronic fields. Herein, the large scale (21 cm × 15 cm) high-quality single layer graphene (SLG) and multilayer graphene on a flexible plastic substrate PET were controllably prepared through layer-by-layer (LBL) transfer using the thermal release adhesive transfer method (TRA-TM). Transmission and antibending performance based on PET/GE were superior to traditional PET/ITO. The square resistance of a nine-layer graphene electrode reached approximately 58 Ω. Combined with our newly developed and highly effective Fe₃O₄@RGO (reduced graphene oxide) catalyst, the power conversion efficiency of the dye-sensitized solar cell (DSC) using flexible PET/GE conductive substrate was comparable to that of the DSC using the PET/ITO substrate. The desirable performance of PET/GE/Fe₃O₄@RGO counter electrodes (low-cost indium- and platinum-free counter electrodes) is attributed to the interfacial compatibility between 2D graphene composite catalyst (Fe₃O₄@RGO) and 2D PET/GE conductive substrate. In addition, DSCs that use only PET/GE (without Fe₃O₄@RGO catalyst) as counter electrodes can also achieve a photocurrent density of 6.30 mA cm^–2. This work is beneficial for fundamental research and practical applications of graphene and graphene composite in photovoltaics, photocatalytic water splitting, supercapacitors

Layered and Pb-Free Organic–Inorganic Perovskite Materials for Ultraviolet Photoresponse: (010)-Oriented (CH₃NH₃)₂MnCl₄ Thin Film

Organic–inorganic lead perovskite materials show impressive performance in photovoltaics, photodetectors, light-emitting diodes, lasers, sensors, medical imaging devices, and other applications. Although organic–inorganic lead perovskites have shown good performance in numerous fields, they contain toxic Pb, which is expected to cause environmental pollution in future large-scale applications. Thus, the photoelectric properties of Pb-free organic–inorganic perovskite materials should be developed and studied. In this paper, we report on the photoresponse of Pb-free organic–inorganic hybrid manganese perovskite (CH₃NH₃)₂MnCl₄. To the best of our knowledge, this study demonstrates the first time that organic–inorganic hybrid manganese perovskites are used for this type of application. We found that the solution-processed MA₂MnCl₄ thin film tends to be oriented along the <i>b</i>-axis direction on the TiO₂ surface. The evident photoresponse of the FTO/TiO₂/MA₂MnCl₄/carbon electrode devices was observed under 10–30 Hz flashlight frequencies and a 330 nm light beam. This simple, green, and low-cost photoresponsive device is beneficial for the future industrial production of optical recorders and optical memory devices