| CdTe/CdS solar cell is accepted as a high efficiency, low-cost, stable, and advantage for large-scale manufacture, it recently becomes the focus hi the photovoltaic filed. But the key problem to fabricate CdTe solar cells is to form a stable ohm contact to p-CdTe with back electrode. The intention of the paper is to study the deposition and properties of ZnTe(ZnTe:Cu) polycrystalline thin films and to apply ZnTe(ZnTe:Cu) as a complex back contact layer between CdTe and metal electrode to obtain ohm contact and high efficiency CdTe solar cells.The changes of the structure, optical and electrical properties of ZnTe(ZnTe:Cu) polycrystalline thin films deposited by co-evaporation with cooper concentration and annealing temperature have been systematically studied. The crystal phase of as-deposited ZnTe(ZnTe:Cu) films depends on the Cu concentration in ZnTe. ZnTe films with un-doped Cu and low Cu doped (2.98%) show cubic phases with preferred orientation of (111). Heavily Cu-doped films exhibit a mixture of cubic and hexagonal phases. Phase transition takes place in the annealing process. The morphology of ZnTe:Cu is also Cu concentration and annealing temperature dependent. The Cu doping efficiency, the conductivity and the grain size of the filmscould be greatly improved after annealing in a N2 environment with fast reaching higher temperature.That ZnTe/ZnTe:Cu layer used as a complex back contact improves the performance of CdTe solar cells has been studied. CdTe solar cells with the complex back contacts do not have roll-over. Effects of un-doped layer thickness, doped concentration and post-deposition annealing temperature of the complex layer on solar cells performance have been studies. The results show that ZnTe/ZnTe:Culayer can improve back contacts and largely increase the conversion efficiency of CdTe solar cells under the same technical condition. Using the complex back contact, a small CdTe cell of 73.14% fill factor and 12.93% conversion efficiency has been obtained.
|
PDF Full Text Request