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

Abstract

Mixed-halide perovskites, CH 3 NH 3 PbI 3−x Cl x , 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, CH 3 NH 3 PbI 3 . 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.

Multifunctional CNT:TiO2 additives in spiro‐OMeTAD layer for highly efficient and stable perovskite solar cells

“…Since the seminal work in 2009, 1 perovskite solar cells (PSCs) based on organic‐inorganic halide perovskite ABX 3 (A = CH 3 NH 3 + , Cs + ; 2‐5 B = Sn 2+ , Pb 2+ ; 6,7 X = Cl − , I − , Br − 8‐11 ) have shown a dramatic increase in power conversion efficiency (PCE) from the initial 3.8% PCE to the currently certified 25.5% PCE, 12 which makes them comparable to the PCE of polycrystalline silicon solar cells. At present, PSCs can be classified into three types according to their architectures, namely, planar heterojunction, mesoscopic heterojunction, and bulk heterojunction architectures.…”

Simple, Robust, and Going More Efficient: Recent Advance on Electron Transport Layer‐Free Perovskite Solar Cells

“…However, the small charge-carrier diffusion length within the polycrystalline perovskite film relative to the grating electrode spacing can limit the device performance. [110] The lateral Al/MAPbI 3−x Cl x /MoO 3 /Au device gives a highest PCE of 2.4% (Figure 7l). [127] Such a nonsymmetric backcontacted device platform is also helpful for understanding the effect of film morphology on the optoelectrical property and the final device performance.…”

“…[36] Inserting interdigitated back-contact electrodes into PSCs overcomes the optical losses by eliminating the need for transparent electrodes and low architectural defect tolerance present Adv. [110] Copyright 2018, Wiley-VCH. 2019, 9,1900248 Reproduced with permission.…”

“…k) Device structure, l) J – V curves, and m) the current density as a function of the gap distances. Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

“…Such a nonsymmetric back‐contacted device platform is also helpful for understanding the effect of film morphology on the optoelectrical property and the final device performance. For example, to reveal the effects of Cl − on the performance of the final devices, Cho and co‐workers fabricated lateral device (Figure k) with perovskite with and without Cl − to observe charge carrier diffusion and found that the charge carrier pathways in the mixed‐halide perovskite with a longer charge carrier diffusion length are more efficient . The lateral Al/MAPbI 3− x Cl x /MoO 3 /Au device gives a highest PCE of 2.4% (Figure l).…”