Thickness dependence of a CuI hole transport layer on initial photostability and photovoltaic performance of organic solar cells

Abstract

Phone: þ82 2 940 8675, Fax: þ82 2 942 9160Understanding the effects of interlayers in organic photovoltaic devices is necessary to investigate its potential to maximize efficiencies. Here, we investigate how a solutionprocessed copper (I) iodide (CuI) hole transport layer (HTL) prepared onto indium tin oxide (ITO) substrates affects the photovoltaic performances of the devices based on Poly(3hexylthiophene-2,5-diyl) (P3HT):Phenyl-C61-butyric acid methyl ester (PCBM), with its different thicknesses. We found that the film morphology and roughness depends sensitively on the concentration of CuI solutions used for thin films. The surface of CuI films spun with high concentration solutions consists of large grains with high roughness, resulting in a direct short in the devices. For the devices with a thin CuI layer, the power conversion efficiency (PCE) of the devices under illumination was observed to decrease with time. The X-ray photoelectron spectroscopy (XPS) suggests that the indium ions might be diffused into the active layer across the thin CuI layer. Our results highlight that the CuI layer thickness is a key parameter in affecting not only efficiency but also device yield and short-term photostability.

Hole Transport Bilayer for Highly Efficient and Stable Inverted Perovskite Solar Cells

“…The bilayer’s hysteresis is comparable to that of the PTAA-only devices (Figure S2a,d); PEDOT:PSS-based devices showed no hysteresis. These results are consistent with observations in the literature that points to CuI’s morphology as a possible source of hysteresis. , …”

“…These results are consistent with observations in the literature that points to CuI's morphology as a possible source of hysteresis. 34,35 In a p−i−n device architecture, the underlying HTL influences perovskite films' morphology and crystallinity. Therefore, to understand the improvement in device performance in bilayer-containing devices, we imaged the morphology and grain size of the as-prepared perovskite films on different HTLs using AFM (Figure 2a−d).…”

Water Adsorption Enhances Electrical Conductivity in Transparent P-Type CuI

“…(c) Compilation of work function values measured in previous studies. Star markers are used for KP measurements. − Triangle markers are used for UV photoemission spectroscopy (UPS) measurements. ,− …”

“…Even though the bulk structure of CuI is unaffected by exposure to ambient air and humidity, properties of crucial importance for TCM applications (e.g., electrical conductivity and work function) can be sensitive to much smaller amounts of adsorbed water or oxygen than the quantities necessary for bulk reactions. Previous work on stability of the electrical conductivity in CuI focused only on long time scales (weeks or months). , In a similar fashion, the CuI work function reported in several papers was measured after an undefined exposure time to air, without investigating the effect of oxygen or moisture on the work function of a pristine CuI surface. ,− In this work, we investigate changes in the conductivity, work function, and ionization energy of CuI in the first few hours of exposure to air at different relative humidities (RH).…”

Observing Charge Transfer Interaction in CuI and MoS2 Heterojunction for Photoresponsive Device Application

“…The integration of the TMDCs layered materials with gallium nitride and silicon carbide semiconductors has been investigated for optoelectronic device applications. , However, most of the oxide and nitride based wide bandgap semiconductors are normally n-type, whereas the counterpart TMDC layers are normally p-type. The γ-copper iodide (γ-CuI) with p-type conductivity is one of the notable halide wide bandgap (∼3.1 eV) semiconductors with 2D sheetlike structures and can be significant to integrate with n-type TMDC layered semiconductors. − γ-CuI with excellent hole-transporting property has a great prospect in high efficiency solar cells, photosensors, and other device applications. , The charge transfer interaction and formation of effective junction potential in p-type γ-CuI and n-type TMDCs layers are still to be explored for fabrication of efficient optoelectronic device components. In this prospect, we explored the possibility of fabricating γ-CuI/MoS 2 based heterojunction and its interface properties for developing a photoresponsive device.…”