Abstract
Solution-processed CdTe nanocrystals solar cells have attracted much attention due to their low cost, low material consumption, and potential for roll-to-roll production. Among all kinds of semiconductor materials, CdS exhibits the lowest lattice mismatch with CdTe, which permits high junction quality and high device performance. In this study, high quality CdS nanocrystals were prepared by a non-injection technique with tetraethylthiuram disufide and 2,2′-dithiobisbenzothiazole as the stabilizers. Based on the CdTe and CdS nanocrystals, devices with the architecture of ITO/ZnO/CdS/CdTe/MoOx/Au were fabricated successfully by a solution process under ambient condition. The effects of annealing conditions, film thickness, and detailed device structure on the CdTe/CdS nanocrystal solar cells were investigated and discussed in detail. We demonstrate that high junction quality can be obtained by using CdS nanocrystal thin film compared to traditional CdS film via chemical bath deposition (CBD). The best device had short circuit current density (Jsc), open circuit voltage (Voc) and fill factor (FF) of 17.26 mA/cm2, 0.56 V, and 52.84%, respectively, resulting in a power conversion efficiency (PCE) of 5.14%, which is significantly higher than that reported using CBD CdS as the window layer. This work provides important suggestions for the further improvement of efficiency in CdTe nanocrystal solar cells.
Highlights
Thin film solar cells based on solution-processed semiconductor nanocrystals (NCs) have many advantages such as wide spectra response from ultraviolet to infrared [1], low cost, environmental-friendly process, and potential development to roll-to-roll large area production [2,3,4,5,6].With the progress of nanomaterials fabrication techniques, various high quality semiconductor NCs have been synthesized and investigated
Efficient CdTe thin film solar cells are always fabricated with a hetero-junction configuration, that is, CdTe works as the donor and CdS [15,16], ZnSe [17], ZnS [18], as well as ZnO [19] serve as the acceptors
Efficiency up to 22.1% [20] and an open circuit voltage up to 1 V [21] were demonstrated by using a CdTe/CdS hetero-junction configuration
Summary
Thin film solar cells based on solution-processed semiconductor nanocrystals (NCs) have many advantages such as wide spectra response from ultraviolet to infrared [1], low cost, environmental-friendly process, and potential development to roll-to-roll large area production [2,3,4,5,6].With the progress of nanomaterials fabrication techniques, various high quality semiconductor NCs have been synthesized and investigated. Efficient CdTe thin film solar cells are always fabricated with a hetero-junction configuration, that is, CdTe works as the donor and CdS [15,16], ZnSe [17], ZnS [18], as well as ZnO [19] serve as the acceptors. In 2005, Gur et al [22] first reported the solution-processed CdTe/CdSe NC hetero-junction solar cells with a power conversion efficiency (PCE) of ~3%. This device architecture was further investigated by optimizing the device processing technology and device structure (using an inverted structure such as ITO/ZnO/CdSe/CdTe/Au instead of the normal structure of ITO/CdTe/CdSe/Al)
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