Engineering Band‐Type Alignment in CsPbBr₃ Perovskite‐Based Artificial Multiple Quantum Wells

Abstract

Semiconductor heterostructures of multiple quantum wells (MQWs) have major applications in optoelectronics. However, for halide perovskites—the leading class of emerging semiconductors—building a variety of bandgap alignments (i.e., band‐types) in MQWs is not yet realized owing to the limitations of the current set of used barrier materials. Here, artificial perovskite‐based MQWs using 2,2′,2″‐(1,3,5‐benzinetriyl)‐tris(1‐phenyl‐1‐H‐benzimidazole), tris‐(8‐hydroxyquinoline)aluminum, and 2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline as quantum barrier materials are introduced. The structures of three different five‐stacked perovskite‐based MQWs each exhibiting a different band offset with CsPbBr3 in the conduction and valence bands, resulting in a variety of MQW band alignments, i.e., type‐I or type‐II structures, are shown. Transient absorption spectroscopy reveals the disparity in charge carrier dynamics between type‐I and type‐II MQWs. Photodiodes of each type of perovskite artificial MQWs show entirely different carrier behaviors and photoresponse characteristics. Compared with bulk perovskite devices, type‐II MQW photodiodes demonstrate a more than tenfold increase in the rectification ratio. The findings open new opportunities for producing halide‐perovskite‐based quantum devices by bandgap engineering using simple quantum barrier considerations.

Plasmonic Nb2CTx MXene-MAPbI3 Heterostructure for Self-Powered Visible-NIR Photodiodes

“…To evaluate the performance of the Nb 2 C T x -based photodetectors, we obtained their photoresponsivity ( R ) and specific detectivity ( D* ). These figure-of-merits are estimated following previous reports, , and defined as where P in is the power of the incident light, A is the active area (0.04 × 1 mm 2 ), B is the bandwidth, and i n is the noise current. For planar Nb 2 C T x photodetectors, the shot noise ( i s ) is predominant because of the large dark current, leading to i n = i s = , where q is the elementary charge.…”

“…To evaluate the performance of the Nb 2 CT x -based photodetectors, we obtained their photoresponsivity (R) and specific detectivity (D*). These figure-of-merits are estimated following previous reports, 35,36 and defined as…”

Optical Properties of Perovskite‐Organic Multiple Quantum Wells

“…In contrast to our observations, Lee et al, measured much larger energy shifts for the same perovskite thicknesses in single quantum well structures. [15,26] Assuming variations in the perovskite thickness, charge carriers are expected to accumulate at positions with slightly higher well thickness so they can minimize their energy. The relatively high values of surface roughness obtained via XRR (Table S1, Supporting Information) are in agreement with this effect.…”

“…As sketched in Figure S6, Supporting Information, a simple 1D step-like potential is assumed which represents the potential curve of the conduction band for electrons or the valence band for holes. Well heights of 0.41 eV in the conduction band and 0.55 eV in the valence band were assumed, [26] and the effective masses in the well were set to 0.15 m e for electrons and 0.14 m e for holes. [30] Solving the eigenvalue problem results in multiple eigenenergies for each well thickness.…”

Quantum Tunneling Effect in CsPbBr3 Multiple Quantum Wells

“…As displayed in Figure e,g (right axes), the SQW photodetectors made of 5 nm thick BCP layers have demonstrated a 10-times higher R and 7-times higher EQE and D* , further illustrating the effect of the barrier thickness-dependent shorter CS time on the photoelectric behavior of the SQW. The calculations were performed following previous reports, − as summarized in the Table S2.…”