We have studied four 2D layered perovskites, including OA2PbI4 (RP phase), ODAPbI4 and BDAPbI4 (DJ phase), (GA)MAPbI4 (ACI phase), where OA is [(C m H2m+1)NH3](m = 8), ODA is [NH3(CH2) m NH3](m = 8), BDA is [NH3(CH2) m NH3](m = 4), and GA is [C(NH2)3]; RP, DJ, and ACI means Ruddlesden–Popper, Dion–Jacobson and alternating cations in the interlayer, respectively. The temperature dependence of absorption and photoluminescence (PL) spectra have been measured. From which the average phonon energy (electron-phonon interaction strength) is analyzed as around 34 (80), 47 (184), 50 (402), and 63 (758) with the unit of meV for OA2PbI4, ODAPbI4, BDAPbI4, and (GA)MAPbI4, respectively. Larger phonon energy indicates the involvement of more phonons in organic spacer layer, with the corresponding stronger electron-phonon interaction. Furthermore, ultrafast transient absorption spectroscopy proves that, when the excitation photon energy is serval hundred meV higher than bandgap, the excitons still are the major photoexcitations in OA2PbI4, but polarons are major one in ODAPbI4, BDAPbI4, and (GA)MAPbI4 films, no matter the excitonic transitions dominate the absorption at their band edges. This work proves the organic spacers can regulate electron–phonon interaction then optoelectronic properties in 2D perovskites profoundly, which have implications toward future rational design for relevant devices.

中文翻译：

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层状钙钛矿稳态激子跃迁与超快极化子光激发的比较：电子-声子相互作用的作用

我们研究了四种二维层状钙钛矿，包括 OA2个铅4个（RP 阶段），ODAPbI4个和 BDAPbI4个(DJ 相), (GA)MAPbI4个（ACI 阶段），其中 OA 是 [(C 米 H2个米+1)氨氮3个](米= 8), 官方发展援助是 [NH3个(CH2个) 米 氨氮3个](米= 8), BDA 为 [NH3个(CH2个) 米 氨氮3个](米= 4), GA 为 [C(NH2个)3个]; RP、DJ 和 ACI 分别表示 Ruddlesden–Popper、Dion–Jacobson 和夹层中的交替阳离子。已经测量了吸收和光致发光 (PL) 光谱的温度依赖性。从中分析出OA的平均声子能量（电子-声子相互作用强度）约为34（80）、47（184）、50（402）和63（758），单位为meV2个铅4个, ODAPbI4、BDAPbI4个, 和 (GA)MAPbI4个， 分别。较大的声子能量表明更多的声子参与有机间隔层，相应地更强的电子-声子相互作用。此外，超快瞬态吸收光谱证明，当激发光子能量比带隙高数百 meV 时，激子仍然是 OA 中的主要光激发2个铅4个, 但极化子是 ODAPbI 中的主要一种4个, 二溴二苯醚4个, 和 (GA)MAPbI4个薄膜，无论激子跃迁主导其带边的吸收。这项工作证明有机间隔物可以深刻地调节二维钙钛矿中的电子-声子相互作用和光电特性，这对未来相关设备的合理设计具有重要意义。