Rubidium Iodide-Doped Spiro-OMeTAD as a Hole-Transporting Material for Efficient Perovskite Photodetectors

Abstract

2,2′,7,7′-Tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD) is one of the broadly used hole transport materials for high-performance perovskite photodetectors. However, to achieve high hole mobility and conductivity, it often requires the addition of additives and dopants with hygroscopic properties similar to bis­(trifluoromethane)­sulfonamide lithium salt (Li-TFSI) and 4-tert-butylpyridine (TBP), which are forced to undergo aggregation and hydrolysis under environmental conditions, hence leading to pinholes/voids in resultant films. In this work, we added rubidium iodide (RbI) to spiro-OMeTAD together with Li-TFSI and TBP, and the complexation between RbI and TBP prevented the evaporation of TBP that hinders the aggregation of Li-TFSI and reduces the undesired voids. Consequently, RbI-doped spiro-OMeTAD serves as the hole transport layer (HTL) for perovskite photodetectors, enhancing the conductivity and hole transport abilities of the hole transport layer, which also helps to promote energy-level matching with the perovskite layer. The performance of the perovskite photodetector is verified by analyzing the current density–voltage characteristics as well as the transient and dynamic photocurrent response characteristics. Devices with RbI-doped HTLs exhibit a champion specific detectivity approaching 3.77 × 1013 Jones and a linear dynamic range of 114 dB. This work provides a feasible approach to improve the stability of small-molecule-based hole transport materials for perovskite photodetectors.

AlGaN‐Based Solar‐Blind Ultraviolet Detector with a Response Wavelength of 217 nm

“…External quantum efficiency (EQE) is calculated as the ratio of the number of carriers flowing in the external circuit to the number of photons incident on the external circuit. It can be calculated by the equation [ 10 ] where P in represents the incident light intensity, J ph is the photocurrent density, h is Plank's constant, J dark stands for the dark current density, e is the electric charge, and v is the photon frequency.…”

“…External quantum efficiency (EQE) is calculated as the ratio of the number of carriers flowing in the external circuit to the number of photons incident on the external circuit. It can be calculated by the equation [10] EQE ¼…”

Understanding different oxidation methods for the hole transport layer Spiro-OMeTAD to improve perovskite solar cell performance

“…We further investigated the crystal structure of the PVSK/Spiro-OMeTAD sample using x-ray diffraction spectroscopy (XRD). The peak positions of the PVSK/Spiro-OMeTAD films were similar with that of the pure PVSK films; all the XRD patterns exhibited prominent diffraction peaks at 14.5°, 20.5°, 24.0°, 25.0°, 28.8°, 32.3°, 41.1°, and 43.6°, which were corresponding to (110), ( 112), ( 211), ( 202), ( 220), (310), (224), and (314) of MAPbI 3 perovskite, respectively (figure 5) [38,39]. The MAPbI 3 /Spiro-OMeTAD films show similar crystal structures with about negligible differences in peak intensity.…”

Simultaneous Improvement in Photovoltaic Performance and Air Stability of Perovskite Solar Cells by Controlling Molecular Orientation of Spiro-OMeTAD

“…12 Several researchers have introduced new additives for Spiro-OMeTAD to improve the photovoltaic performance and operational stability of PSCs. These include (i) doping rubidium iodide (RbI) into Spiro-OMeTAD together with Li-TFSI and TBP, which prevented the aggregation of Li-TFSI; 13 (ii) adding acetonitrile (ACN) to the Spiro-OMeTAD to improve the electrical contact between the perovskite and Spiro-OMeTAD layers; 14 (iii) using metal−organic framework Zn-CBOB-doped Spiro-OMeTAD to enhance the conductivity of the HTL and prevent water; 15 and (iv) mixing 4-(trifluoromethyl)pyridine (TFP) in the Spiro-OMeTAD to enhance moisture resistance. 16 In addition to these great efforts on increasing hole density in the Spiro-OMeTAD layer by preventing moisture absorption, improving the hole transport in the HTL through controlling molecular orientation is another way to improve hole conductivity in the HTL because molecular orientation affects μ h of organic semiconductors.…”

“…Several researchers have introduced new additives for Spiro-OMeTAD to improve the photovoltaic performance and operational stability of PSCs. These include (i) doping rubidium iodide (RbI) into Spiro-OMeTAD together with Li-TFSI and TBP, which prevented the aggregation of Li-TFSI; (ii) adding acetonitrile (ACN) to the Spiro-OMeTAD to improve the electrical contact between the perovskite and Spiro-OMeTAD layers; (iii) using metal–organic framework Zn-CBOB-doped Spiro-OMeTAD to enhance the conductivity of the HTL and prevent water; and (iv) mixing 4-(trifluoromethyl)­pyridine (TFP) in the Spiro-OMeTAD to enhance moisture resistance …”