The paper by Xing et al. (2014) presents the development of low-temperature solution-processed wavelength-tunable perovskites for lasing applications. The authors, including Michael Grätzel and Subodh Mhaisalkar, describe the optical properties, trap states density, and temperature-dependent effects of CH₃NH₃PbI₃ thin films. Key findings include: 1. **Optical Properties**: CH₃NH₃PbI₃ films exhibit strong absorbance from UV to near-infrared (800 nm) with two distinct peaks at 480 nm and 760 nm, indicating excellent light harvesting capabilities. The room temperature photoluminescence quantum yield (PLQY) and gain measurements were also reported. 2. **Trap States Density**: The study determined the trap states density in CH₃NH₃PbI₃ thin films, finding bulk traps with fast trapping times and surface/interfacial traps with slow trapping times. The total trap density is estimated to be around \(2 \times 10^{17} \, \text{cm}^{-3}\). 3. **FDTD Simulations**: Finite difference time domain (FDTD) simulations demonstrated that the PCBM layer significantly improves light confinement in CH₃NH₃PbI₃ films, enhancing the propagation of polarized light components. 4. **Temperature-Dependent Effects**: Temperature-dependent studies showed that CH₃NH₃PbI₃ remains stable over a wide temperature range, with minimal changes in PL spectra and ASE threshold. This stability is attributed to its low trap states density and temperature-invariant charge carrier diffusion. 5. **Additional Applications**: The authors also explored the potential of CH₃NH₃PbI₃ for solar cells and flexible substrates, demonstrating green ASE from CH₃NH₃PbBr₃ on PET substrates. Overall, the research highlights the potential of CH₃NH₃PbI₃ as a promising material for low-temperature solution-processed lasing applications.The paper by Xing et al. (2014) presents the development of low-temperature solution-processed wavelength-tunable perovskites for lasing applications. The authors, including Michael Grätzel and Subodh Mhaisalkar, describe the optical properties, trap states density, and temperature-dependent effects of CH₃NH₃PbI₃ thin films. Key findings include: 1. **Optical Properties**: CH₃NH₃PbI₃ films exhibit strong absorbance from UV to near-infrared (800 nm) with two distinct peaks at 480 nm and 760 nm, indicating excellent light harvesting capabilities. The room temperature photoluminescence quantum yield (PLQY) and gain measurements were also reported. 2. **Trap States Density**: The study determined the trap states density in CH₃NH₃PbI₃ thin films, finding bulk traps with fast trapping times and surface/interfacial traps with slow trapping times. The total trap density is estimated to be around \(2 \times 10^{17} \, \text{cm}^{-3}\). 3. **FDTD Simulations**: Finite difference time domain (FDTD) simulations demonstrated that the PCBM layer significantly improves light confinement in CH₃NH₃PbI₃ films, enhancing the propagation of polarized light components. 4. **Temperature-Dependent Effects**: Temperature-dependent studies showed that CH₃NH₃PbI₃ remains stable over a wide temperature range, with minimal changes in PL spectra and ASE threshold. This stability is attributed to its low trap states density and temperature-invariant charge carrier diffusion. 5. **Additional Applications**: The authors also explored the potential of CH₃NH₃PbI₃ for solar cells and flexible substrates, demonstrating green ASE from CH₃NH₃PbBr₃ on PET substrates. Overall, the research highlights the potential of CH₃NH₃PbI₃ as a promising material for low-temperature solution-processed lasing applications.