Photoluminescence Quenching Simulator (PLQ−Sim) is a user-friendly software to study the photoexcited state dynamics at the interface between two organic semiconductors forming a blend: an electron donor (D), and an electron acceptor (A). Its main function is to provide substantial information on the photophysical processes relevant to organic photovoltaic and photothermal devices, such as charge transfer state formation and subsequent free charge generation or exciton recombination. From input parameters provided by the user, the program calculates the transfer rates of the D/A blend and employs a kinetic model that provides the photoluminescence quenching efficiency for initial excitation in the donor or acceptor. When calculating the rates, the user can choose to use disorder parameters to better describe the system. In addition, the program was developed to address energy transfer phenomena that are commonly present in organic blends. The time evolution of state populations is also calculated providing relevant information for the user. PLQ−Sim is license free software that can be run via dedicated webserver nanocalc.org or downloading the program executables (for Unix, Windows, and macOS) from the PLQ-Sim repository on GitHub.