how to convert equation in lambert w function

I= I_L - I_(o ) [e^((q(V+I*R_s )/a*k*T) )-1] - (V+I*R_s)/R_sh I want to solve this equation to know the value of R_s, a, R_sh using lambert w function. Except these three unknown all other parameters are known. Basically this equation is solar cell one diode model equation. Actually sir this is an implicit equation and i want to convert it in a explicit function in the form of I and V using lambert w function so please help how it can be convert in this form actually sir i am attaching you one paper so that you can tell me how they convert it explicit form so in that paper i want to know how they convert equation (1) in to equation (2)

[Walter Roberson]

duplicates http://uk.mathworks.com/matlabcentral/answers/266295-how-to-solve-equation-using-lambert-w-function