Exploring a Fatigue‐Free Layered Hybrid Perovskite Ferroelectric for Photovoltaic Non‐Volatile Memories

Abstract

Through a functional unit‐transmutation strategy, a fatigue‐free layered hybrid perovskite ferroelectric (C6H5CH2NH3)2CsPb2Br7 (BCPB) has been developed, which demonstrates stable spontaneous polarization (Ps) of 6.5 μC cm−2 and high Curie temperature up to 425 K. Meanwhile, BCPB shows splendid bulk photovoltaic effect (BPVE) properties with noticeable zero‐bias photocurrent density (5 μA cm−2), and high on/off switching ratio of current (over 3×105); these merits even overmatch the most known ferroelectric semiconductor BiFeO3. The unique structure with self‐regulated net electrical charged layers gives rise to the fatigue‐free feature of Ps and BPVE (no significant fatigue after 108 polarity switching cycles), promoting the potential applications of BCPB in photovoltaic non‐volatile memories. This work offers an efficient approach for exploring fatigue‐free semiconducting ferroelectrics as well as excavates their further applications in next‐generation electronic devices.

Shedding Light on the Stability and Structure–Property Relationships of Two-Dimensional Hybrid Lead Bromide Perovskites

“…Ferroelectricity has been reported in several hybrid, layered lead bromide and monolayer lead chloride perovskites, such as with C4BrN2, where the ferroelectric reversal polarization behavior is noted as evidence of this property, along with the noncentrosymmetric crystal structure and Curie temperature phase transition. ,,,,,,,,,,− For 2D perovskites, the structural origin of the recorded ferroelectric spontaneous polarization is reported to be associated with the orientation of the C–N bonds in the organic spacer molecules, with respect to the inorganic slab layers. , Specifically, the structures feature the C–N bonds of the ammonium cations aligning in the same direction that results in a net dipole. We proceeded to probe the existence of ferroelectric response in our titled materials by employing switching spectroscopy piezoresponse force microscopy (SS-PFM) measurements ,,,,− at room temperature for thin films of the C6BrN2, C7BrN2, and C8BrN2 compounds.…”

“…The only studied bulk, multilayer lead bromide perovskites are based on the common short guanidinium, ethylammonium, propylammonium, and butylammonium, as well as one reference with hexylammonium, as the A′-site spacer cation, tuned to give n = 2 or 3 layer members, but single-crystal structural data is scarce. ,− Specifically, 2D perovskites incorporating butylammonium-based cations include (CH 3 (CH 2 ) 3 NH 3 ) 2 (MA) n– 1 Pb n Br 3 n +1 ( n = 1–3), (CH 3 (CH 2 ) 3 NH 3 ) 2 (FA)­Pb 2 Br 7 , (CH 3 (CH 2 ) 3 NH 3 ) 2 (Cs)­Pb 2 Br 7 , (CH 3 (CH 2 ) 3 NH 3 ) 2 (Cs)­Pb 3 Br 10 , and ((CH 3 ) 2 CHCH 2 NH 3 ) 2 (CH 3 CH 2 NH 3 )­Pb 2 Br 7 with isobutyl­ammonium (CH 3 ) 2 CHCH 2 NH 3 . ,− ,, The 2D lead bromide perovskites incorporating ethylammonium-based cations include (C 2 H 8 N) 4 Pb 3 Br 10 , a unique three-layered perovskite with [100] orientation where ethylammonium occupies both A- and A′-site cation positions, and the [110]-orientated perovskite with hydroxy­ethyl­ammonium (HO­(CH 2 ) 2 NH 3 ) 2 (FA) 2 Pb 2 Br 8 . , Recently, a report of 2D hybrid lead bromide perovskites of the Dion–Jacobson structure described incorporating cyclic diammonium cations . Moreover, most of these 2D lead bromide perovskites examined report ferroelectricity as a property. ,,,,,− ,− …”

Stimuli-responsive switchable halide perovskites: Taking advantage of instability

“…Analogous effects due to cation reorientations have been observed in 2D perovskites as well, such as (BZA)2PbCl4 (where BZA + is benzylammonium), (CHA)2PbBr4 (where CHA + is cyclohexylammonium), (AMP)PbI4 (where AMP 2+ is 4-(aminomethyl)piperidinium) (Figure 3 D), and others. [64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82] Importantly, such cation reorientations may also be accompanied with structural changes of the inorganic framework. In particular, copper-based 2D perovskites undergo strong Jahn-Teller distortions upon temperature changes.…”

“…An analogous ferroelectric-to-paraelectric transition due to cation disordering was also observed in 2D perovskites (Figure 8 A). [64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82] Interestingly, in addition to ferroelectric behavior, such 2D perovskites also display semiconducting properties which could be useful for next-generation applications. For instance, ferroelectric photovoltaic devices would be able to produce anomalous high open-circuit voltages and efficient charge separation due to the built-in field of the ferroelectric polarization.…”

“…An analogous device based on (BZA)2CsPb2Br7 perovskite achieved remarkable 10 8 switching cycles between two polarization states without showing significant fatigue. 76 Such a long cycling stability is highly essential for memory device applications.…”