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The CO2reduction reaction (CO2RR) is an essential step in natural photosynthesis and artificial photosynthesis to provide carbohydrate foods and hydrocarbon energy in the carbon-neutral cycle. However, the current solar conversion efficiencies and/or product selectivity of the CO2RR are very sluggish due to its complicated multiple-step charge transfer reactions. Here, we systematically investigate the charge transfer reaction rate during CO2reduction on CuBi2O4photocathodes, where the surface is modified with 3-aminopropyltriethoxysilane (APTES). We discover that the surface amine group increases the charge separation rate, significantly enhancing the surface charge transfer reaction rate. However, the surface acidity has less influence on the first-order reaction, indicating that a rate-determining step (RDS) exists in the early stage of the photoelectrochemical cell (PEC) processes. Moreover, the intensity-modulated photocurrent spectroscopy (IMPS) confirms that both surface charge transfer and the recombination rate on APTES-coated CuBi2O4are larger than bare CuBi2O4while possessing comparable charge transfer efficiencies. Overall, the surface charge transfer reactions under the PEC condition require designing more effective nanostructured photoelectrodes and powerful characterization methods to intrinsically increase the charge separation and transfer rate while reducing the recombination rate.

In addition to device flexibility, the retentivity performance of photoelectric materials after an extreme reverse-bending process is intrinsically important and desirable for next-generation advanced flexible optoelectronics. In this work, we designed and fabricated large-area flexible SnS2thin films with a novel nanosheet/amorphous blended structure to achieve an outstanding flexible photoelectric performance via a facile evaporation and post-thermal annealing route. Crystal structure analysis showed that the obtained SnS2thin films were constructed with nanosheets oriented parallel to the substrate which were surrounded and connected by the amorphous component with a smooth surface. This nanosheet/amorphous blended structure allowed extreme bending because of the adhesive and strain-accommodation effect that arises from the amorphous components. The assembled SnS2flexible photodetectors can bear a small bending radius as low as 1 mm for over 3000 bending–flatting cycles without a drastic performance decay. In particular, over 90% of the initial photoelectric responsivity (40.8 mA/W) was maintained even after 1000 bending–flatting cycles. Moreover, the SnS2thin film can convert photons to photocurrent over a wide spectral range from ultraviolet to near infrared. These unique characteristics indicate that the strategy used in this work is attractive for the development of future wearable photoelectric and artificial intelligence applications.

The transfer and recombination of photoinduced charge carriers play the crucial roles in a photoelectric conversion system. In this work, the Ag2S/fluorine-doped tinoxide (FTO) was used as the platform to understand the photoinduced charge carrier transfer and recombination at the light absorber and electrode interface. SnS2was evaporated onto the FTO surface to cooperate the Fermi level with Ag2S, which reduced the Schottky barrier at the Ag2S/FTO interface. Kelvin probe force microscopy measurements reveal that the Fermi level of FTO can be tuned from −4.93 to −4.75 eV by various SnS2with different evaporation amounts. Transient surface photovoltage tests confirm that the recombination of the photogenerated charge carrier can be drastically suppressed. The photoelectric conversion efficiency of the resulting solar cell devices has been significantly improved.