Effect of surface recombination in high performance white-light CHNHPbI single crystal photodetectors.

Methylammonium lead iodide (CHNHPbI), with the organic-inorganic hybrid perovskite (OIHP) structure, has gained tremendous research interest due to its excellent photo-electron conversion ability in the application of photovoltaics. Despite its solution processed polycrystalline thin film form in solar cells, the single crystalline counterpart may offer some incredibly novel optoelectronic functionalities. In this work, a sizable (>5 mm) and high quality CHNHPbI single crystal has been synthesized by the inverse temperature crystallization method, and a white-light photodetector of the structure glass/ITO/Ga/ CHNHPbI/Au was fabricated. Overbroad photo-excitation intensities ranging from 0.1 mW/cm to 100 mW/cm using a sun-light simulator, the on-off ratio is tunable in a wide-range from 65 to 2250 at zero bias voltage. The responsivity (R) and detectivity (D*) are 36.2 mA/W and 2.68×10 Jones respectively at a weak white-light intensity such as 0.1 mW/cm. Both the photodetective parameters decrease with the increase of the illumination intensity. Based on impedance spectra obtained at working condition and light intensity dependent J measurements, the surface trap-assist recombination may play a dominating role. The corresponding lifetime (τ) and resistance (R) exhibit fast decays at higher illumination intensities. This fundamental study may pave the way for exploring the contribution of the surface trap-assist recombination in the CHNHPbI single crystal based photodetector. We believe it is applicable for integration in micro-photonics for sensitive and weak white-light photo-detection.