In thin film solar cells, due to production cost concern, the semiconductor materials usually contain multiple impurity/defect states as donor and acceptor dopants. Local charge neutrality (LCN) condition is proposed to determine the equilibrium Fermi level and concentration of electrons and holes. A general equation of LCN is expressed as which is a transcendental equation of EF. It is impossible to find its analytical solution and the equation can only be solved by using graphic or numerical method. We proposed a simple approximate graphic method (GM) for estimation of majority carrier compensation of semiconductors with multiple donors and multiple acceptors. By introducing the concept of ranking of the dopants and wrapping step function, the approximate concentration and Fermi level could be obtained easily. In this work, we analyse the graphic method and propose a new numericgraphic method (NGM) based on GM. Comparison of NGM with numerical method (NM) and analytics of accuracy of GM are made. With the help of numerical calculation, some procedures of GM which allow a wilder rang of application of GM are improved.
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