Giant electric field dependent hole mobility of CsPbBr₃ nanocrystal films

Colloidal CsPbBr₃ nanocrystals are emerging as solution-processed semiconductors to fabricate advanced optoelectronic devices. The carrier mobility of nanocrystal films plays a crucial role in determining the performance of these devices. In this work, we studied hole- and electron-only devices based on CsPbBr₃ nanocrystals with different sizes. The zero field hole and electron mobilities of CsPbBr₃ nanocrystal films show size dependence. The zero field hole mobility increases from 0.39 × 10^-9 to 2.62 × 10^-9 cm² V^-1 s^-1 and the zero field electron mobility increases from 0.54 × 10^-8 to 4.36 × 10^-8 cm² V^-1 s^-1 with their average diameter increasing from 9 nm to 26 nm. With the electric field increasing from 0 to 50 MV m^-1, the hole mobility of CsPbBr₃ nanocrystal films increases by 2-3 orders of magnitude. The electric field dependent coefficient (α), which describes the electric field dependence of the hole mobility, decreases from 6.5 × 10^-4 to 5.0 × 10^-4 with increasing size. In addition, we also determined the carrier mobility of CsPbBr₃ nanocrystals with different ligands. By combining the calculation of charging energy, Monte Carlo simulations and Wentzel-Kramers-Brillouin approximation, we also theoretically illustrate the influence of size, ligand and electric field on the hole mobility of CsPbBr₃ nanocrystals. The insights into the hole mobility of CsPbBr₃ nanocrystals provides a great chance to design new generation nanocrystal based devices.