Investigations on the physical origin of lateral photovoltage in PbS-colloidal quantum dot/Si heterojunctions

Abstract

Restricted area heterojunctions, an array of lead sulfide colloidal quantum dots (PbS-CQDs) and crystalline silicon, are studied with a non-destructive remote contact light beam induced current (RC-LBIC) technique. As well as getting good quality active area images we observed an anomalous unipolar signal response for the PbS-CQD/n-Si devices and a conventionally expected bipolar signal profile for the PbS-CQD/p-Si devices. Interestingly, our simulation results consistently yielded a unipolar and bipolar nature in the signals related to the PbS-CQD/n-Si and PbS-CQD/p-Si heterostructures, respectively. In order to explain the physical mechanism involved in the unipolar signal response of the PbS-CQD/n-Si devices, we propose a model based on the band alignment in the heterojunctions, in addition to the distribution of photo-induced excess majority carriers across the junction. Given that the RC-LBIC technique is well suited to this context, the presence of these two distinct mechanisms (the bipolar and unipolar nature of the signals) needs to be considered in order to have a better interpretation of the data in the characterization of an array of homo/heterojunctions.

An insight into optical beam induced current microscopy: Concepts and applications

“…In another work, the group further utilized RC‐OBIC technique using a 670 nm diode laser system to investigate the current profile of restricted area lead sulphide colloidal quantum dots and single crystal silicon (PbS‐CQDs/Si) heterojunctions. They were also able to record the distribution of the majority carriers across the junction resolving up to 200 μm (Abhale et al, 2016).…”