Visualization and Investigation of Charge Transport in Mixed‐Halide Perovskite via Lateral‐Structured Photovoltaic Devices

• Published in: Advanced functional materials 2018-10, Vol.28 (41), p.n/a
• Main Authors: Yang, Seok Joo, Kim, Min, Ko, Hyomin, Sin, Dong Hun, Sung, Ji Ho, Mun, Jungho, Rho, Junsuk, Jo, Moon‐Ho, Cho, Kilwon
• Format: Article
• Language: English
• Subjects: Atomic force microscopy; Carrier lifetime; Carrier recombination; charge carrier pathway; Charge transport; Chlorine; Current carriers; Diffusion; Diffusion length; Electrical properties; lateral perovskite solar cells; Materials science; mixed‐halide perovskite; Morphology; Optoelectronic devices; Osmosis; Perovskites; Photoelectric effect; Photoelectric emission; Photovoltaic cells; Solar cells; Spectroscopic analysis
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201804067

Mixed‐halide perovskites, CH3NH3PbI3−xClx, can be used to fabricate highly efficient perovskite solar cells; the presence of chlorine ions affects the perovskite morphology and enhances optoelectronic properties. However, the reported device performances of mixed‐halide perovskites are comparable to those of triiodide perovskites, CH3NH3PbI3. Thus, the benefits of the presence of Cl− ions in mixed‐halide perovskites are uncertain. To clarify the effects of Cl− on the optoelectronic properties of perovskite devices, a suitable device structure is required. In this study, lateral‐structured perovskite devices are fabricated and their electrical properties are investigated. A clear contrast is found between the optoelectronic properties of the mixed‐halide and triiodide perovskite; a suitable platform is also constructed for the spectroscopic analysis. Scanning photocurrent spectroscopy is used to visualize the charge carrier diffusion in the perovskite films and it is found that the charge carrier diffusion length of the mixed‐halide perovskite is longer. It is also demonstrated by using conducting atomic force microscopy that the charge carrier pathways in the mixed‐halide perovskite are more efficient, which means that it has longer charge carrier recombination life‐times and higher photocurrents. This lateral‐structured device has an architecture that makes it suitable for the observation of charge carrier diffusion and spectroscopic analysis. Charge carrier transport properties of triiodide and mixed‐halide perovskite films are investigated by using lateral‐structured perovskite solar cells. Mixed‐halide perovskite contains more efficient charge carrier pathway and less grain boundaries than triiodide perovskite. It results in longer charge carrier diffusion lengths and recombination life‐time, which induces the improved current density and performance along the gap distances between the electrodes.