Studying the charge carrier properties in CuInS_2 films via femtosecond transient absorption and nanosecond transient photocurrents

The carrier behavior in CuInS_2 thin films at femtosecond and microsecond time scales is discussed in detail. Transient absorption data suggests that the photo-generated carriers relax rapidly accompanied by a change in energy. The photogenerated charge carriers are extracted by a bias electric field E in the nanosecond transient photocurrent system. An applied E improves the efficiency of photon conversion to charge carriers and enhances the velocity of the extracted charge carriers. In addition, there exists a threshold of illumination intensity in the extraction process of charge carriers in the CuInS_2 thin film, above which carrier recombination occurs. The corresponding loss further increases with illumination intensity and the recombination rate is almost independent of E. Our results provide useful insights into the characteristics of carriers in the CuInS_2 thin film and are important for the operation of optoelectronic devices realized with these films.

Carbonized polymer dots enhanced stability and flexibility of quasi-2D perovskite photodetector

Quasi-2D perovskites have been demonstrated to be competitive materials in the photodetection fields due to the enhanced moisture stability by large organic cations.However,as the increasing demands of modern technology,it is still challenging to combine the flexibility with the capability of weak light detection in a low-cost way.Here,amides,carboxylic acids,and anhydrides groups-rich carbonized polymer dots(CPDs)were employed to fll in the perovskite grain boundaries,which can passivate the point defects of perovskite by coordinating with the unbonded Pb atoms,and reduce the leakage current.Weak light detection capability was demonstrated by directly resolving light with an intensity of 10.1 pW cm^(-2).More importantly,the stretchable polymer chains on CPDs strongly interact with perovskite ions through multiple supramolecular interactions,and extend the stretchable properties to the perovskite/CPDs composites,which can maintain the integral structure stability during the deformation of perovskite crystals and restricted any crack by releasing the flm strain.Our fabricated devices show extraordinary flexible stability in the bending-dependent response tests.The viscoelasticity of CPDs improves the bending stability of the flexible quasi-2D perovskite photodetectors,and device performance shows no degradation after bending 10000 times,comparable or even outperforming the dominating flexible photodetectors.