Nano Lett. 16, 1009–1016 (2016)

Adding the chemical element guanidinium to perovskite solar cells can enhance charge-carrier lifetime and the cell's open circuit voltage, report researchers from the University of California at Los Angeles. It is known that non-radiative charge-carrier recombination at grain boundaries limits the performance of these solar cells and thus a means for eliminating this phenomenon is highly desirable. The team describe how guanidinium-based additives serve to passivate recombination centres at grain boundaries leading to superior performance with cell power conversion efficiencies greater than 17% and an open circuit voltage of 1.1 V. It is believed that the guanidinium ions suppress formation of iodide vacancies in the perovskite material and that their hydrogen bonding capabilities passivate iodine species at grain boundaries.