Study of trapping and recombination processes in thin films of MAPbI3, MAPbI2Br and MAPbI2Cl through photoconductivity measurements

Trapping and recombination processes in thin films of MAPbX3 (X is I, Br or Cl) were studied by means of transient photoconductivity measurements and theoretical simulation of the photocurrent response; in particular the influence of temperature, intensity of illumination and pressure inside the measurement system on the transient photocurrent were studied. The study revealed that the photocurrent of thin films of MAPbI3, MAPbI2Br and MAPbI2Cl measured at atmospheric pressures is mainly affected by surface transient photocurrent, whereas the photocurrent resulting from measurements performed in vacuum is mainly governed by bulk trap states. It was also found that, in general the surface processes are delayed whereas the bulk processes gives raise to fast recombination. The results allowed to establish also, that the transport in MAPbI3, MAPbI2Br and MAPbI2Cl films is affected by both recombination attributed to deep trap states and trapping processes attributed to shallow trap states.