Owing to the superior properties of hybrid perovskite, it is possible to avoid some of the selective layers in perovksite solar cells (PSCs). One known example is the so-called hole-conductor-free PSCs, which were discovered at the beginning of the perovskite race. In this work, we introduce a thin MoO3 layer, in HTM-free PSCs, at the perovskite/gold interface in order to investigate its influence on photovoltaic (PV) performance and to study the charge extraction behavior, recombination lifetime, and effect of hysteresis. Charge extraction measurements show that implementing a MoO3 layer results in more charges to be extracted; this is beneficial to its PV performance. Intensity-modulated photovoltage spectroscopy shows two characteristic times at high and low frequency. The high frequency is dependent on light intensity and is related to the charge carrier recombination in the perovskite, whereas the low frequency is independent of light intensity and might be related to ion diffusion. Finally, it was observed that the MoO3 forms a noncontinuous layer on the perovskite surface, which on the one hand improves its PV performance but on the other hand does not provide a physical barrier at this interface. This work provides new insights on HTM-free PSCs and the importance of their interfaces.
Bibliographical noteFunding Information:
We would like to thank the Israel Ministry of Energy for financial support and Dr. Monika Rai for the EQE measurements.
© 2018 American Chemical Society.