Influence of defects and dopants on the photovoltaic performance of Bi2S3: first-principles insights. Issue 13 (13th March 2017)

• Record Type: Journal Article
• Authors: Han, Dan; Du, Mao-Hua; Dai, Chen-Min; Sun, Deyan; Chen, Shiyou
• Is Part Of: Journal of materials chemistry. Volume 5:Issue 13(2017)
• Page Start: 6200
• Page End: 6210
• Publication Date: 2017-03-13
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c6ta10377d
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : First-principles calculations show that the photovoltaic efficiency of solar cells using Bi2 S3 as the light absorber is intrinsically limited by its point defects, while Cu, Br and Cl doped Bi2 S3 may be an ideal n-type electron acceptor or counter electrode material. Abstract : Bi2 S3 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 Bi2 S3 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 Bi2 S3, 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 Bi2 S3 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 Bi2 S3 nanocrystals in p-PbS/n-Bi2 S3 nano-heterojunction solar cells may be type-inverted into p-type due to Pb doping, with a buried p–n junction formed in the Bi2 S3 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 Bi2 S3 may be an ideal n-type electron acceptor or counter electrode material, while the performance of Bi2 S3 as a light-absorber or sensitizer material is intrinsically limited.