Abstract
Perovskite photovoltaics offer a compelling combination of extremely low-cost, ease of processing and high device performance. The optoelectronic properties of the prototypical CH3NH3PbI3 can be further adjusted by introducing other extrinsic ions. Specifically, chlorine incorporation has been shown to affect the morphological development of perovksite films, which results in improved optoelectronic characteristics for high efficiency. However, it requires a deep understanding to the role of extrinsic halide, especially in the absence of unpredictable morphological influence during film growth. Here we report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled. The chlorine incorporation is found to mainly improve the carrier transport across the heterojunction interfaces, rather than within the perovskite crystals. Further optimization according this protocol leads to solar cells achieving power conversion efficiency of 17.91%.
Highlights
Perovskite photovoltaics offer a compelling combination of extremely low-cost, ease of processing and high device performance
It remains challenging for the perovskite PV community to achieve a deep understanding of its composition, crystal structure and defect-associated optoelectronic properties for further device performance improvements
CH3NH3PbI3 À xClx has been serving as a typical system to examine the role of extrinsic ions, from the point of view of both crystallography and film morphology
Summary
Perovskite photovoltaics offer a compelling combination of extremely low-cost, ease of processing and high device performance. We report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled. Measurements based on time-resolved photoluminescence (TRPL), Kelvin-probe force microscopy (KPFM), transient photovoltage decay and capacitance–voltage (CV) indicate that the chlorine incorporation affects carrier transport across heterojunction interfaces rather than within the perovskite crystals. These results indicate a tremendous opportunity for rational incorporation of extrinsic elements in perovskites as desired, which facilitates their implementation for practical use in next-generation PV devices
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