Cadmium Selenide Based Photovoltaic Devices And Methods For Forming The Same
AssigneeFirst Solar, Inc.
InventorsTursun Ablekim, Sachit Grover, James Hack, Elline Hettiaratchy, Taylor Hill, Sergei Kniajanski, Wyatt Metzger, Nicholas Valdes, Gang Xiong
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Abstract
Provided are photovoltaic devices with polycrystalline type II-VI semiconductor absorber materials including n-type absorber compositions and having p-type hole contact layers are described herein. Methods of treating semiconductor absorber layers and forming hole contact layers are described.
Claims29
A tandem photovoltaic device comprising an upper submodule over a lower submodule, wherein the upper submodule comprises:
- an absorber layer consisting essentially of CdSe, wherein:
- the absorber layer is n-type;
- the absorber layer has an n type carrier concentration of less than 1×1017 cm−3;
- and
- the absorber layer includes chlorine in grain boundaries at a level equal to or greater than 1×1013 cm−3 in the grain boundaries as measured by secondary-ion mass spectrometry;
- and
- a hole contact forming a p-n junction with the absorber layer.
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A method for forming an absorber layer of a photovoltaic device comprising:
- providing a layer stack comprising a p-type layer;
- depositing a polycrystalline film over the p-type layer, wherein the polycrystalline film consists essentially of CdSe;
- contacting an exposed surface of the polycrystalline film with a halogen compound and an accelerant;
- heating the polycrystalline film in a controlled environment to form the absorber layer, wherein the controlled environment comprises oxygen and selenium, whereby:
- the absorber layer has an n type carrier concentration of less than 1×1017 cm−3;
- and
- the absorber layer includes chlorine in grain boundaries at a level equal to or greater than 1×1013 in the grain boundaries.
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A method for forming a photovoltaic device comprising:
- annealing an absorber layer consisting essentially of CdSe in the presence of a halogen compound, whereby a grain size of the absorber layer grows and halogen diffuses into the absorber layer;
- and
- treating the absorber layer by heating in a controlled environment comprising Se and O2, whereby the treating reduces Se vacancies in the absorber layer.
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Dependencies are inferred from the claim text.