Recently, CsPbX3 (X = Cl, Br, and I) perovskite quantum dots (QDs) have exhibited significant potential for application in the field of lighting. However, their self-absorption and agglomeration significantly decrease their photoluminescence when their solution is centrifuged to form a powder; this hinders their applications in the field of solid-state lighting. Currently, there is lack of efficient solutions to overcome the self-absorption issue for CsPbX3 QDs. Thus, herein, an effective strategy is proposed via the in situ growth of CsPbBr3 (CPB) QDs in a mesoporous silica (m-SiO2) matrix, where self-absorption originating from the agglomeration of the QD powder is distinctly suppressed in the m-SiO2 matrix. Furthermore, due to its higher transmissivity, some photons can transport along the channels of m-SiO2 with less light loss. As a result, the photoluminescence quantum yield (PLQY) of 68% for the CsPbBr3/m-SiO2 (CPB/MS) powder is distinctly higher than that of the discrete CPB powder (36%). In addition, the chemical stability, thermal quenching and luminous decay were evidently improved for the CPB/MS nanocomposite. Finally, a remote flexible light-emitting diode with ultrahigh stability and arbitrary bending angle was achieved, which presented a pathway for the application of CPB QDs in solid-state lighting.