Abstract
The complicated and diverse deep defects,voids,and grain boundary in the CZTSSe absorber are the main reasons for carrier recombination and efficiency degradation.The further improvement of the open-circuit voltage and fill factor so as to increase the efficiency of CZTSSe device is urgent.In this work,we obtained K-doped CZTSSe absorber by a simple solution method.The medium-sized K atoms,which combine the advantages of light and heavy alkali metals,are able to enter the grain interior as well as segregate at grain boundary.The K-Se liquid phase can improve the absorber crystallinity.We find that the accumula-tion of the wide bandgap compound K2Sn2S5 at grain boundary can increase the contact potential differ-ence of grain boundary,form more effective hole barriers,and enhance the charge separation ability.At the same time,K doping passivates the interface as well as bulk defects and suppresses the non-radiative recombination.The improved crystallinity,enhanced charge transport capability and reduced defect den-sity due to K doping result in a significant enhancement of the carrier lifetime,leading to 13.04％device efficiency.This study provides a new idea for simultaneous realization of grain boundary passivation and defect suppression in inorganic kesterite solar cells.
维普
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