Toward High-Performance Electron/Hole-Transporting-Layer-Free, Self-Powered CsPbIBr₂ Photodetectors via Interfacial Engineering

Abstract

Self-powered photodetectors (PDs) with inorganic lead halide perovskites hold multiple traits of high sensitivity, fast response, independence from external power supply, and excellent sustainability and stability, thus holding a great promise for practical applications. However, they generally contain high-temperature-processed electron-transporting layers (ETLs) and high-cost, unstable hole-transporting layers (HTLs) coupled with noble metal electrodes, which bring significant obstacles of production cost and stability for their potential commercialization. Herein, we demonstrate the building of high-performance HTL/ETL-free, self-powered CsPbIBr2 PD with simplified architecture of fluorine-doped tin oxide (FTO)/CsPbIBr2/carbon upon interfacial modification by polyethyleneimine (PEI). The optimized PD yields a dark current of 2.03 × 10–9 A, peak responsivity (R) of 0.32 A/W, maximum specific detectivity (D*) of 3.74 × 1012 Jones, and response time of 1.21 μs. These figures of merit are far beyond those of the one prepared without PEI modification and even the PD containing TiO2 ETL. Hence, our work suggests a highly feasible route to develop self-powered PDs with significantly simplified fabrication and a reduced production cost.

Charge-Transporting-Layer-Free, Vacuum-Free, All-Inorganic CsPbIBr2 Perovskite Solar Cells Via Dipoles-Adjusted Interface

“…Noting that because of the relatively large work function of FTO, the recombination between extracted electrons in it and holes in CsPbIBr 2 film happens easily, which generally leads to interior performance of the resulting PSC. Our previous study has shown that the introduction of PEI between the FTO and perovskite layer can effectively lower the FTO work function value from 4.52 to 4.25 eV [ 12 ], as also being verified below. Thus, the back-flow of electrons in FTO can be suppressed significantly, and the enhanced performance of the corresponding CsPbIBr 2 PSC can be expected.…”

“…After the PEI modification (8 mg/mL), the FTO surface potential is obviously improved. A lower work function generally appears with a higher surface potential [ 12 , 27 ]. Therefore, it can be concluded that the work function of FTO has been reduced by the PEI modification, which leads to the more aligned band energies between the work function of FTO and the conduction energy level of CsPbIBr 2 .…”

“…Additionally, the results were fitted with a one RC-element equivalent circuit model, wherein the radius of the semicircular curve implies a recombination resistance (R rec ), reflecting the recombination of charge carriers at the interface [ 14 , 34 ]. As shown in Figure 4 b, the larger R rec for the PSC with PEI modification demonstrates that there is a lower carrier recombination rate at the interface for it [ 12 ]. This may be one of the reasons for its larger V oc and FF .…”

“…However, in view of the organic-inorganic hybrid perovskite special composition, it has the intrinsic instability against oxygenation, high temperature, and/or humidity [ 7 , 8 , 9 ]. Therefore, many researchers have recently shifted their research focus to the inorganic perovskite, which has better stability than the hybrid halide perovskite [ 10 , 11 , 12 , 13 ], and at the same time has the potential to achieve an excellent photoelectric performance as the organic-inorganic hybrid halide perovskite. The pursuit of a low-cost and high-performance inorganic PSC is becoming the research hot point in the research field of perovskite devices.…”

High‐Performance Flexible Self‐Powered Photodetectors Utilizing Spontaneous Electron and Hole Separation in Quasi‐2D Halide Perovskites

“…[27] Besides, the commonly used electron transport layers, such as TiO 2 , need to be annealed at a relatively high temperature over 400 °C, which is incompatible with most device substrates of flexible photodetectors. [28,29] In addition, the high-performance organic materials based hole transport layer, including spiro-MeOTAD, PTAA, and PEDOT:PSS, are not only deliquescent but also expensive, which are not the appropriate device materials for large-scale fabrication. [30,31] As a result, there is an urgent need to break this bottleneck to achieve a cost-effective scheme to construct the highly-efficient flexible self-powered photodetectors with a simple device configuration.…”