Optical Characterization Of Organic Halide Perovskite Films And Application In Photodetector

With unique combination of simple synthetic procedures,long exciton diffusion lengths,and high charge carrier mobilities,the organo-lead halide perovskites have recently attracted intensive scientific interests.In addition to their potential applications in solar cells,the organo-lead halide perovskites could work effectively as optical signal amplifying materials,suitable for many optoelectronics such as the light-emitting diodes,lasers,and photo-detectors.To obtain the high quality laser emitted form perovskite,organo-lead halide perovskite single crystal is more often used compared with the perovskite films,owing to the simple laser mode they generated,such as Fabry-Perot(FP)mode or Whispering gallery(WG)mode.While the latter one is more likely to emit random lasers which have low quality factor,thus is difficult to modify and control.Even though perovskite single crystals demonstrate excellent laser charateristics,their long preparation periods,complicated preparation process,and fixed crystal-shape expose the disadvantages in applications.For solving these problems,a facile and low-cost spin-coating method to prepare high-quality organo-lead perovskite is reported in this paper.After pumping by femtosecond laser,the particles in perovskite films could emit WG-like mode laser.Although the quality factor of laser is much smaller than the one generated by single crystal,the laser actions show an independence on the particles size.By the optical characterizations and simulation,it is confirmed that the peculiar shape of perovskite particles gives the opportunities to form the high order WG-like mode resonance.In order to well control the size and laser actions of perovskite films,the perovskite microdisk arrays with extremely uniform size are demonstrated via spinning the perovskite precursor solution on the patterned substrates.And by changing the concentration of perovskite precursor solution or the diameter of silicon microdisks,the size of perovskite microdisks can be well adjusted.Based on a large number of experiments,it is found that uniform perovsite microdisk arrays are reproduceable with this robust method.Meanwhile,the laser properties of different perovskite microdisks on the same wafer exhibited uniformity,including the mode spacing,the wavelength of laser peaks and threshold.Associated with optical experiments and numerical calculations,it is proved that the WG mode laser were emitted by perovskite microdisks.In addition to the studies on laser actions of perovskite films,the optoelectronic properties are investigated.A patterned substrate with grating structure was firstly fabricated by photolithography,induced couple plasma etching and electron-beam evaporation.Then a simple perovskite based photodetector was fabricated via coating the perovskite films on the gold grating.Under the illumination of continuous-wave laser and applied bias voltage,the performances of perovskite photodetector,such as the response time,the relationship between photocurrent and voltage or illumination power density,external quantum efficiency,were fully studied.It is noteworthy that the rise and decay time of the device are both as small as 8.3 ms,which exhibits a promising potential in on-chip scale photodetector.