recombination is still lacking-even for the most studied perovskite MAPbI 3 , for example, which could limit their further developments. Exciton effect plays a critical role in optoelectronic devices, such as photovoltaic cells, LEDs, and lasers. [11,12] The strength of electron-hole interaction is characterized by exciton binding energy. For photovoltaic cells, the exciton binding energy needs to be overcome for producing free electrons and holes to contribute to the photocurrent. Therefore, exciton binding energies below thermal energies at room temperature (RT) are highly desirable (<26 meV). [13] While for LEDs and lasers, a relative larger exciton binding energy is needed to obtain an efficient near-band-edge exciton emission at a wide range of temperatures (≈60 meV for semiconductor ZnO). [14] To date, great efforts have been made to determine the exciton binding energy of perovskite MAPbI 3 . [15][16][17][18][19] However, such an important physical parameter obtained from various experiments distributes in a wide range from 2 to 55 meV, which is a disadvantage of an accurate understanding of the photophysical properties of perovskites and their further applications.Along with the exciton binding energy, carrier recombination is another important issue in semiconductors. [20] Previous reports focused on this question that whether free carriers (FCs) or excitons are the dominant recombination specie in perovskites. Both FC recombination [5,16,21] and exciton recombination [22][23][24] were attributed to the RT photoluminescence (PL) of MAPbI 3 . Further investigations indicate the recombination behavior in perovskites has a close relation with the excitation intensity. [15,19,25,26] Moreover, several reports found the PL intensity shows square dependence on the excitation intensity, suggesting the FC recombination is dominant in PL processes. [19,26] However, He et al. [27] have argued that when a relatively high excitation level (photocarrier density (n 0 ) > 10 15 cm −3 ) is applied, the exciton binding energy decreases due to the screening effect of the large amount of photogenerated FCs. They also demonstrated that under an excitation level close to the working regime of solar cells (≈5 × 10 14 cm −3 ), the PL A typical aggregation-induced emission luminogen (AIE-gen) is introduced into perovskite CH 3 NH 3 PbI 3 and the material and photophysical properties of hybrid films are investigated with absorption, X-ray diffraction, and steadystate photoluminescence (PL) characterization. When excited by a high photon flux (4.08 × 10 22 cm −2 s −1 ) laser beam (3.82 eV) at room temperature, the CH 3 NH 3 PbI 3 polycrystalline thin films exhibit dual emission locating at 1.64 eV (P 1 ) and 1.59 eV (P 2 ). The two PL peaks are attributed to free carrier (FC) recombination and exciton recombination, respectively. Additionally, an introduction of AIE-gen changes the peak value ratio of P 1 :P 2 , indicating the radiative recombination ratio of FCs versus excitons in perovskite films can be tuned with this method. S...