Polymer‐Assisted Phase Stable γ‐CsPbI₃ Perovskite Film for Self‐Powered and Ultrafast Photodiodes

Abstract

are essential for reliable and sensitive photodetection. [7] Nowadays, prospective thin film photodetectors are flourishing as promising candidates for applications in next-generation wearable [8] and transparent electronics, [9] soft robotics, [10] and health monitoring. [11] Notably, thin film photodetectors own performance advantages over conventional counterparts as photoexcited charge carriers can be transported faster and more effectively as the thickness of active layer could be scaled down to nanoscale. [12] For example, the 20 nm CH 3 NH 3 PbBr 3 single crystalline thin film photodetector with detectivity of 6.59 × 10 [11] Jones and responsivity of 5600 A W −1 has been obtained; [13] Wu et al. reported high-performance photodetector with a responsivity of 3.15 A W −1 and a detectivity of 3.94 × 10 12 Jones using a 150 nm active layer. [8] Perovskite photoactive materials have gained considerable attention from academic and industrial sectors, owing to their excellent properties, [1] such as very high absorption coefficient, good defect tolerance, large diffusion length, facile bandgap tunability, and simple solution-processability. Among various perovskite compositions, CsPbI 3 (α phase and γ phase) offers suitable bandgap (E g ) of 1.7 eV for visible light-harvesting, [14] which is beneficial for diverse applications in optoelectronics. However, black-phase CsPbI 3 could inevitably undergo phase transition to yellow phase (δ phase, E g ≈ 2.8 eV) at room temperature. [15] It remains challenging to process the blackphase CsPbI 3 with enhanced ambient phase-stability at room temperature.Strategies of stabilizing the black phase of CsPbI 3 perovskite includes synthesis of nanoparticles with long chain ligands [16] and incorporation of polymer additives. [17][18][19] Majority of research works focused on the low-dimension form of CsPbI 3 such as nanotubes, [20] nanowires, [21] and quantum dots, [22] of which all ask for complicated synthesis method as well as stateof-the-art tools for photodetector device fabrication, leading to their high cost and low reproducibility. Alternatively, introducing polymer additives have become promising ways to stabilize the perovskite structure and improving the performance of perovskite-based photovoltaics. [23] They are effective in freezing counterions' migration and manipulating perovskite crystalline formation via strong bonding interactions between functional groups and crystalline cations. [24][25][26][27] Bansode et al. demonstrated Lead-halide perovskite materials have emerged as promising alternatives for optoelectronic applications due to their low-cost, easily tunable bandgaps, and facile solution-processability. Despite all their exciting merits, perovskite materials are currently suffering the stability issues, such as moisture and oxygen-induced rapid degradation and phase transition. In this work, γ phase CsPbI 3 perovskite thin films with compact grain boundaries and improved ambient stability are successfully developed via introducing poly-2-ethyl-2-oxazolin...

All-inorganic perovskite film photodetectors with tailored deposition techniques and component engineering

“…138 However, the phase transition from the cubic CsPbI 3 (black a-phase) to the yellow phase (d phase, with E g E 2.8 eV) at room temperature presents a significant obstacle to further development. 139,140 By incorporating an ITO/SnO 2 /CsPbI 3 /Au configuration on a flexible PET substrate, the fabricated PD showcased an on/off photocurrent ratio of approximately 10 3 A W À1 and a specific detectivity of 10 12 Jones. Similarly, Chen et al achieved highly stable CsPbI 3 films by adding 12 wt% PVP to the precursor.…”