Air‐Stable and Self‐Driven Perovskite Photodiodes with High On/Off Ratio and Swift Photoresponse

Abstract

Recent years have witnessed rapid developments in organic-inorganic hybrid perovskites, among which 2D Ruddlesden-Popper (RP) perovskites stand out due to their outstanding ambient stability. In photodetector applications, 2D RP perovskites are mostly limited to lateral device configuration because of their preferred in-plane charge transportation within quantum well structures. In this work, the low-temperature solution construction of 2D RP perovskite-based photodiodes in vertical device architecture is demonstrated. The paradigm phenylethylamine (PEA) spacer cation-based 2D perovskites are fabricated and optimized by exploiting a combination of a NH Cl additive and dimethyl sulfoxide solvent (DMSO) solvent. They show increased crystallinity, extended photoluminescence lifetimes, and importantly a generation of 3D phases embedded within 2D perovskites, which efficiently promotes charge transfer. As a result, the photodetectors exhibit a high on/off ratio up to 2 × 10 , a large photocurrent of 0.34 mA cm , and rapid rise (5.8 ms) and decay time (4.6 ms). Of critical importance is the outstanding film/device stabilities demonstrated by storage in air (at 25 °C with 60% relative humidity) for 15 days as well as under UV illumination for 1.5 h and after 1500 bending cycles on flexible substrate.

Benefiting from Spontaneously Generated 2D/3D Bulk‐Heterojunctions in Ruddlesden−Popper Perovskite by Incorporation of S‐Bearing Spacer Cation

“…The PL decays of both PEA and TEA samples can be best fitted by a biexponential function in Equation :where A 1 and A 2 are the amplitudes, τ 1 and τ 2 are the PL decay times. According to our previous studies in 2D perovskites,] τ 1 corresponds to the PL quenching from fast nonradiative recombination which is induced by defects or impurities introduced during preparation of grains or interphase charge transfer. The slower time constant τ 2 represents radiative recombination of the charge carriers.…”

“…According to our previous studies in 2D perovskites, [31] the exciton diffusion length (L D ) was measured as shown in Figure 4b with the inset illustrating the measurement setup. According to our previous studies in 2D perovskites, [31] the exciton diffusion length (L D ) was measured as shown in Figure 4b with the inset illustrating the measurement setup.…”

“…Compared to the PEA counterparts, the TEA-based devices show a 40% and 35% increase in short-circuit current density (J SC ) for reverse and forward scans and yield a PCE of 7.20%, which is among the highest ones in low-temperature fabricated 2D RP PSCs. [31,41] Therefore, we attempted to exploit the same strategy to further optimize the TEA thin films and the detailed verification regarding the improvement of crystal structure and orientation, film morphology as well as charge carrier dynamics by NH 4 Cl and DMSO treatments can be found in Figures S5−S9 and Table S2 in the Supporting Information. Nevertheless, neat 2D layered perovskite thin films without further modifications present the inherent structural disorder [39] and orientation randomness, [39] both of which not only lead to trap-assisted nonradiative recombination but also restrict charge transport perpendicular to substrate, thus causing serious hysteresis (see Figure S10a in the Supporting Information for details) and limited device performance.…”

“…Specifically, NH 4 Cl functions to promote the crystallization and reduce trap/defect states yet weaken the lattice order of perovskites whereas DMSO acts to retard the crystallization yet improve the vertical orientation of perovskites and optimizes the 2D/3D interfaces, thereby facilitating interphase charge transfer. These two competitive processes achieve an optimal balance in co‐treated device and result in the best device performance . Therefore, we attempted to exploit the same strategy to further optimize the TEA thin films and the detailed verification regarding the improvement of crystal structure and orientation, film morphology as well as charge carrier dynamics by NH 4 Cl and DMSO treatments can be found in Figures S5−S9 and Table S2 in the Supporting Information.…”

Recent developments in flexible photodetectors based on metal halide perovskite

“…Recently, 2D and quais‐2D perovskites have been used in FPDs due to their increased robustness to moisture and solution process. For example, Liang and co‐workers reported 2D (PEA) 2 MA 3 Pb 4 I 13 perovskites by the low‐temperature solution process, in which 3D phases were inserted into 2D perovskite, enhancing cross‐plane charge transfer . Moreover, the 2D perovskites were utilized to fabricate vertically structured photodetector which exhibited a high on/off ratio and swift photoresponse.…”