Influence of Charge Transport and Defects on the Performance of Planar and Mesostructured Perovskite Solar Cells

摘要

Photoinduced charge selective carrier extraction by linearly increasing voltage technique allows straightforward assessment of charge transport properties within planar and mesostructured perovskite solar cells with respect to light intensity and signal delay time. Charge sensitive device architecture is realized through implementation of insulating layer between the anode or cathode to prevent extraction of unwanted type of carriers. Resulting behavior of comparatively efficient mesoporous and planar solar cells exhibits well balanced charge transport with slight dependence of charge mobility on applied laser pulse fluence, for given pulse delay times. Very similar charge carrier mobilities are present within mesoporous devices, whereas holes trail approximately half an order of magnitude behind electrons in planar structured specimens. Moreover, dispersive transport is identified in the electron selective devices with titanium oxide electron transporter, suggesting considerable presence of trapping states at the perovskite interface, whereas no such behavior characterizes planar samples. Variation in delay time between laser pulse and extraction ramp only affects initial charge concentration present within the device, while transient outlay remains unchanged, indicating absence of film charging effect.