Doping-Induced Charge Localization Suppresses Electron-Hole Recombination in Copper Zinc Tin Sulfide: Quantum Dynamics Combined with Deep Neural Networks Analysis.

Abstract

Nonradiative electron-hole recombination constitutes a major route for charge and energy losses in copper zinc tin sulfide (CZTS) solar cells. Using a combination of nonadiabatic (NA) molecular dynamics and deep neural networks (DNN), we demonstrated that electron-hole recombination is notably retarded by doping with Ag and Ag+Cd. The replacement of lighter Cu and/or Zn with heavier Ag and/or Cd reduces the NA coupling by separating electron and hole wave functions. Such replacement suppresses atomic motions and makes the phonon modes move to low-frequency region, which reduces NA coupling further but inhibits decoherence. The small magnitudes of NA coupling beat the long coherence time, delaying the electron-hole recombination from the Ag+Cd-codoping to the Ag doping system compared with pristine CZTS. The NA couplings predicted by the DNN algorithm lead to the time scales in agreement with the direct simulations. The study provides a robust strategy to design high-performance CZTS solar cells.