Perovskites @ UC DAVIS

Abstract to Poster presented at Molecular Foundry

We investigate temperature-dependent transport behavior of photogenerated free carriers and excitons in single-crystal methylammonium lead bromide (MAPbBr3) nanostructures via scanning photocurrent microscopy (SPCM), photocurrent spectroscopy, and spectrally and temporally resolved photoluminescence (TRPL) measurements. While SPCM profiles show a rapid decay of the photocurrent in about 3μm at room temperature as the photoexcitation moves away from the contact. A much longer decay profile becomes significant at temperatures below 220K with rapid recombination near the electrodes. Remarkably, the long decay photocurrent shows a carrier diffusion length of over 110μm, along the nanosecond-scale lifetimes observed in TRPL indicates incredibly large carrier mobility at lower temperatures.  We hypothesize that this kind of long-distance transport is mainly excitonic due to their dipolar, therefore charge-neutral nature. The poster for this project can be found here.

Skills Acquired:

• Work with a Wire Bonder from West Bond

• Photocurrent Microscopy Measurements

  • Scanning Photocurrent Microscopy (SPCM)

  • Circular Photogalvanic Effect measurement  (CPGE)

• Analysis  with MESUX programming 

• Analysis with IGOR programming 

• Atomic Force Microscopy (AFM)

My Emphasis:

Currently collecting and analyzing photo-responsive data from methylammonium halide perovskite single crystals, MAPbI3 and MAPbBr3, by performing Scanning Photocurrent Microscopy (SPCM) and Circular Photogalvanic Effect measurements (CPGE). My current focus is to see the change in the measurements based on the change of the doping of perovskites by modifying the original synthesis method. Our current recipe is producing p-type single crystals that show almost no long photocurrent decay tales in SPCM for MAPbBr3. We think that making an n-type material will produce a long tale in the SPCM profile due to the longer diffusion lengths of the charge carriers. 

Additionally, creating a new recipe to produce a new to our lab completely inorganic perovskite single crystals CsPbBr3, as well as in charge of synthesizing other perovskite crystals of FAPbBr3. 

Advisor:

Dr. Dong Yu: yu@physics.ucdavis.edu