conditional quantum logic gates. [3][4][5] Moreover, the biexciton state can be used to constitute a multilevel system for realizing population inversion that is one of the key elements for lasing. [6][7][8][9][10][11] Till now, biexcitons have been realized mainly in inorganic semiconductor quantum dots, [12][13][14] hetero structure quantum-wells, [15][16][17] and 2D semiconductors. [18][19][20] Lead-halide perovskites of APbX 3 [A = CH 3 NH 3 + (MA) or Cs + and X = I, Br, or Cl] are solution-processed semiconductors with promising properties, such as low trap densities, high photoluminescence (PL) efficiencies, large absorption coefficients, wavelength tunability and long carrier diffusion lengths, enabling great progress in optoelectronics, such as solar cells, [21][22][23][24] photodetectors, [25][26][27][28] LEDs, [29][30][31] and lasers. [32][33][34][35] As electrons and holes can transport in cornersharing lead halide octahedral networks in three directions, the Coulomb interactions between them are weak in 3D perovskites, resulting in a low binding energy of electron-hole pairs (exciton) about dozens of meV. [36] Therefore, biexcitons have been realized only in perovskite nanocrystals with strong quantum confinement. [37][38][39] 2D layered perovskites (LPs) in the formula of L 2 MA n−1 Pb n X 3n+1 (L = long-chain cations, for instance, butylammonium (BA)) naturally form organic-inorganic quantum-well (QW) structures. Effective confinement of electron-hole pairs within [MA n−1 Pb n X 3n+1 ] 2− layer leads to large exciton binding energy about several hundreds of meV. Furthermore, the band gap of LP-QWs can be tuned across the visible spectral range by the QW thickness of [MA n−1 Pb n X 3n+1 ] 2− layers through adjusting the value. [40][41][42][43] Amplified spontaneous emission (ASE) and lasing of LPs were demonstrated mainly based on thin-films that are actually composed of mixed QWs, in which energy funneling from small to large QWs limits the lasing wavelength. [44,45] Recently, Zhang and co-workers reported tunable excitonic lasers from pure-phase (BA) 2 (MA) n−1 Pb n I 3n+1 with larger than 3 and debated biexciton Auger recombination as a nonradiative loss channel. [46] Chen and co-workers reported room temperature tunable excitonic random lasers from purephase (BA) 2 (MA) n−1 Pb n I 3n+1 with = 1, 2, and 3. [47] The mechanism of these two works is excitonic lasing. Biexciton emission and ASE from phase-pure LP-QWs have been reportedThe biexciton is a quasi-particle created from two free excitons and can be applied for basic quantum operations, entangled light sources, and lasers. 2D lead-halide layered perovskites (LPs) naturally form organic-inorganic quantum wells (QWs), leading to high exciton binding energy and tunable band-gaps dependent on the QW thickness of . Although excitonic lasing has been reported for thicker LP-QWs, biexciton emissions and lasers from phase-pure LP-QWs as a function of remain largely unexplored. Here, a facile solution growth method for fabr...

Long persistent luminescence (LPL) materials of SrAl 2 O 4 doped with Eu 2 + or Dy 3 + can maintain emission over hours after ceasing the excitation but suffer from insolubility, high cost, and harsh preparation. Recently, organic LPL of guest-host exciplex systems has been demonstrated via an intermediate charge-separated state with flexible design but poor airstability. Here, we synthesized a nontoxic two-dimensional organic-inorganic metal hybrid halides (OIMHs), called PBA 2 [ZnX 4 ] with X = Br or Cl and PBA = 4phenylbenzylamine. These materials exhibit stable LPL emission over minutes at room-temperature, which is two orders of magnitude longer than those of previously reported OIMHs. The mechanism study shows that the LPL emission comes from thermally activated charge separation state rather than room-temperature phosphorescence. Moreover, the LPL of PBA 2 [ZnX 4 ] can be excited by low power sources, representing an effective strategy for developing low-cost and high-stability LPL systems.

No abstract

Long persistent luminescence (LPL) materials of SrAl2O4 doped with Eu2+ or Dy3+ can maintain emission over hours after ceasing the excitation but suffer from insolubility, high cost, and harsh preparation. Recently, organic LPL of guest‐host exciplex systems has been demonstrated via an intermediate charge‐separated state with flexible design but poor air‐stability. Here, we synthesized a nontoxic two‐dimensional organic–inorganic metal hybrid halides (OIMHs), called PBA2[ZnX4] with X=Br or Cl and PBA=4‐phenylbenzylamine. These materials exhibit stable LPL emission over minutes at room‐temperature, which is two orders of magnitude longer than those of previously reported OIMHs. The mechanism study shows that the LPL emission comes from thermally activated charge separation state rather than room‐temperature phosphorescence. Moreover, the LPL of PBA2[ZnX4] can be excited by low power sources, representing an effective strategy for developing low‐cost and high‐stability LPL systems.