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.