Field modulation in Na-incorporated Cu(In,Ga)Se2 (CIGS) polycrystalline films influenced by alloy-hardening and pair-annihilation probabilities

Research Institute for Solar and Sustainable Energies (RISE), Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, South Korea. .
Nanoscale Research Letters (Impact Factor: 2.78). 11/2011; 6(1):581. DOI: 10.1186/1556-276X-6-581
Source: PubMed


The influence of Na on Cu(In,Ga)Se2 (CIGS) solar cells was investigated. A gradient profile of the Na in the CIGS absorber layer can induce an electric field modulation and significantly strengthen the back surface field effect. This field modulation originates from a grain growth model introduced by a combination of alloy-hardening and pair-annihilation probabilities, wherein the Cu supply and Na diffusion together screen the driving force of the grain boundary motion (GBM) by alloy hardening, which indicates a specific GBM pinning by Cu and Na. The pair annihilation between the ubiquitously evolving GBMs has a coincident probability with the alloy-hardening event.
PACS: 88. 40. H-, 81. 10. Aj, 81. 40. Cd

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    • "The graded bandgap-induced back-surface field effect, which arises because of the composition dependence of the Ga/(Ga + In) ratio, leads to an increase in the open-circuit voltage (V OC ), fill factor, and short-circuit current density (J SC ) [25] [26]. Na incorporation in CIGS films affects their grain growth and preferred orientation, resulting in small grain size and an increase in V OC [27]. Thus, the current level of understanding of CIGS films is fairly high. "
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