期刊
JOURNAL OF MATERIALS CHEMISTRY A
卷 5, 期 13, 页码 6200-6210出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c6ta10377d
关键词
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资金
- National Natural Science Foundation of China (NSFC) [61574059]
- Shanghai Rising-Star Program [14QA1401500]
- Shu-Guang program [15SG20]
- National Key Research and Development Program of China [2016YFB0700700]
- CC of ECNU
- U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division
Bi2S3 has attracted extensive attention recently as a light-absorber, sensitizer or electron acceptor material in various solar cells. Using first-principles calculations, we find that the photovoltaic efficiency of Bi2S3 solar cells is limited by its intrinsic point defects, i.e., both S vacancy and S interstitial can have high concentration and produce deep defect levels in the bandgap, leading to non-radiative recombination of electron-hole carriers and reduced minority carrier lifetime. Unexpectedly most of the intrinsic defects in Bi2S3, including even the S interstitial, act as donor defects, explaining the observed n-type conductivity and also causing the high p-type conductivity impossible thermodynamically. Doping in Bi2S3 by a series of extrinsic elements is studied, showing that most of the dopant elements such as Cu, Br and Cl make the material even more n-type and only Pb doping makes it weakly p-type. Based on this, we propose that the surface region of n-type Bi2S3 nanocrystals in p-PbS/n-Bi2S3 nano-heterojunction solar cells may be type-inverted into p-type due to Pb doping, with a buried p-n junction formed in the Bi2S3 nanocrystals, which provides a new explanation to the longer carrier lifetime and higher efficiency [Nat. Photonics, 6, 529 (2012)]. Considering the relatively low conduction band and high n-type conductivity, we predict that Cu, Br and Cl doped Bi2S3 may be an ideal n-type electron acceptor or counter electrode material, while the performance of Bi2S3 as a light-absorber or sensitizer material is intrinsically limited.
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