X-Ray Nanoanalysis Revealing the Role of Electronically Active Passivation Layers in Perovskite X-Ray film Detectors

X-ray direct detectors based on hybrid lead-halide perovskite have seen a dramatic increase of interest in the last years. A rush for the achievement of high performing devices drives the scientific community. In this context, several photoconductor sensors employ functional layers to increase the gain effect, but the full comprehension of the mechanism is still lacking. Here X-ray nanoanalysis is used, performed by simultaneous acquisition of X-ray Fluorescence and X-ray Beam Induced Current maps, to investigate at the nanoscale level the role of [6,6]-phenyl-C61-butyric acid methyl ester fullerene (PCBM) molecules when interacting with MAPbI(3) polycrystalline thin films acting as photo-conductors in X-ray detectors. At the device-scale level it shows that the addition of PCBM enhances the X-ray sensitivity by four times. At the nanoscale level how the perovskite grain boundaries act as high photocurrent generation centers is demonstrated. The addition of the PCBM increases the photocurrent generation, as the macroscopic performance does, and the charge collection becomes uniform over the full crystallite volume. The results clarify the role of grain boundaries and charge selecting layers and establish the X-ray nanoanalysis techniques as a powerful tool to investigate charge transport and collection in perovskite films.

Automated summary

X-ray direct detectors based on hybrid lead-halide perovskite have attracted increasing interest in recent years. The goal of achieving high-performance devices has driven the scientific community to study photoconductor sensors employing functional layers. By using X-ray nanoanalysis, this study investigated the interaction between [6,6]-phenyl-C61-butyric acid methyl ester fullerene (PCBM) molecules and MAPbI(3) polycrystalline thin films acting as photo-conductors in X-ray detectors at the nanoscale level. The results showed that the addition of PCBM enhances both the X-ray sensitivity and the charge collection uniformity, clarifying the role of grain boundaries and charge selecting layers in perovskite films.