Persistent photovoltage in methylammonium lead iodide perovskite solar   cells
  Open circuit voltage decay measurements are performed on methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells to investigate the charge carrier recombination dynamics. The measurements are compared to the two reference polymer-fullerene bulk heterojunction solar cells based on P3HT:PC60BM and PTB7:PC70BM blends. In the perovskite devices, two very different time domains of the voltage decay are found, with a first drop on a short time scale that is similar to the organic solar cells. However, two major differences are also observed. 65-70% of the maximum photovoltage persists on much longer timescales, and the recombination dynamics are dependent on the illumination intensity. 
A. Baumann, K. Tvingstedt, M. C. Heiber, S. V\"ath, C. Momblona, H. J.   Bolink, and V. Dyakonov
cond-mat.mtrl-sci