$heatsource is a command for user to solve "time dependent" thermal equation independently without solving Poisson and drift-diffusion equations. This command also needs to go with $xend, $yend, and $heatsolvebytime.
Usually when Poisson and DD solver is solved, the program will calculate the Joule heating, nonradiative recombination as the heatsource. However, sometimes, we may only want to know how the heating affects the temperature.
Therefore, we can assign the heat source in the region assigned $xend, [[$yend] to solve the time dependent thermal equations.
The format is
$heatsource heat_source_start(W/cm) heat_source_end(W/cm) heat_source_step(W/cm)
$heatsolvebytime 1.000e-7 1000 300.00 100 $heatsource 10.0 30.0 5.0 $xend 20.0 100.0 $yend 4.5 3.0