  The Transfer Matrix Method (TMM) has become a prominent tool for the optical
simulation of thin$-$film solar cells, particularly among researchers
specializing in organic semiconductors and perovskite materials. As the
commercial viability of these solar cells continues to advance, driven by rapid
developments in materials and production processes, the importance of optical
simulation has grown significantly. By leveraging optical simulation,
researchers can gain profound insights into photovoltaic phenomena, empowering
the implementation of device optimization strategies to achieve enhanced
performance. However, existing TMM$-$based packages exhibit limitations, such
as requiring programming expertise, licensing fees, or lack of support for
bilayer device simulation. In response to these gaps and challenges, we present
the TMM Simulator (TMM$-$Sim), an intuitive and user$-$friendly tool to
calculate essential photovoltaic parameters, including the optical electric
field profile, exciton generation profile, fraction of light absorbed per
layer, photocurrent, external quantum efficiency, internal quantum efficiency,
and parasitic losses. An additional advantage of TMM$-$Sim lies in its capacity
to generate outcomes suitable as input parameters for electro$-$optical device
simulations. In this work, we offer a comprehensive guide, outlining a
step$-$by$-$step process to use TMM$-$Sim, and provide a thorough analysis of
the results. TMM$-$Sim is freely available, accessible through our web server
(nanocalc.org), or downloadable from the TMM$-$Sim repository (for
\textit{Unix}, \textit{Windows}, and \textit{macOS}) on \textit{GitHub}. With
its user$-$friendly interface and powerful capabilities, TMM$-$Sim aims to
facilitate and accelerate research in thin$-$film solar cells, fostering
advancements in renewable energy technologies.
