A new solar cell structure (a-Si:H/SnS/ZnSe/ITO) is proposed using numerical modelling which has shown an improvement in the experimentally confirmed efficiency of a hydrogenated a-Si based solar cells. The results are obtained by using SCAPS – 1D solar simulator. The thicknesses of both the absorber layers, buffer layer, and window layer are varied to model and optimise the performance of the proposed cell. The optimized structure is also simulated by varying the donor and acceptor densities of the hydrogenated amorphous silicon layer, the operating temperature, and bulk defects. The variation in Voc, Jsc, fill factor, and efficiency of the proposed cell is investigated through simulation. The I-V characteristics and quantum efficiencies of the experimental reference cell (p-i-n a-Si:H), and the optimised proposed cell are compared. The optimised cell shows a considerable increase in efficiency from 11.6 % to 26.91 % and it also shows higher quantum efficiency in larger wavelength bandwidth than the reference model.