Making use of the authors' experimental results and the evidence available in the literature, an alternative model for glass/conducting glass/CdS/CdTe/metal solar cells has been formulated. This model explains the device behaviour in terms of a combination of a hetero-junction and a large Schottky barrier at the CdTe/metal interface. The main experimental observations available to date are described and compared with the currently assumed p–n junction model and this proposed new model. It is shown that the proposed model explains almost all the experimental results more satisfactorily. The paper describes the guidelines to further increase the performance efficiencies based on the new model. Following these new guidelines, the authors have fabricated improved devices producing open circuit voltage (V_oc) values over 600 mV, fill factor (FF) values over 0.60 and the short-circuit current density (J_sc) values over 60 mA cm⁻² for best devices. Although the V_oc and FF could be further improved, the remarkable improvement of J_sc indicates the possibility of further development of multilayer graded band gap tandem solar cells based on CdS/CdTe system.