Progress and prospects of CZTSSe/CdS interface engineering to combat high open-circuit voltage deficit of kesterite photovoltaics: a critical review

Abstract

CZTSSe solar cells are considered to be potential and cost-effective alternative solution to matured photovoltaic technology to meet future energy demands. However, the current performance of CZTSSe solar cells is...

Potential Role of Kesterites in Development of Earth‐Abundant Elements‐Based Next Generation Technology

“…Several back-electrode materials have been explored, including Mo, W, Pd, Ni, and Pt for the kesterite CZTS/Se TFSCs. [9,56] In CIGS TFSCs, Mo as back electrode exhibited excellent adhesion, provided ohmic contact, and offered lower resistance and good chemical stability. [57] The detrimental reaction near the back interface during the sulfurization/selenization process results in MoS/Se 2 formation and the segregation of undesired secondary phases.…”

“…[39] The unfavorable band alignment at the p-n junction increases the carrier recombination and, thereby, reduces the efficiency. [9] The spike-like positive conduction band offset (CBO) or cliff-like CBO with 0-0.4 eV is favorable to achieve high device performance. [81][82][83] Therefore, to improve the band alignment and reduce the interface defect density; different dielectric/metal-oxide ultrathin passivation layers (Al 2 O 3 , SnO 2 , TiO 2 , and Al(OH) 3 ) [65,84,85] between absorber/ buffer and heterojunction heat treatment (HT) processes [86,87] have been applied for kesterite-based devices.…”

“…This kesterite family of materials includes Cu 2 ZnSnS 4 (CZTS), Cu 2 ZnSnSe 4 (CZTSe), and Cu 2 ZnSn(S,Se) 4 (CZTSSe). [ 9 ] The kesterite materials exhibit a high absorption coefficient, p ‐type conductivity, and direct and tunable bandgap. [ 10 ] Thus, kesterite materials have emerged as potential light absorber materials and have exhibited all‐around performance for different applications, as shown in Figure .…”

Enhancing CZTSSe solar cells through electric field induced ion migration

“…4 With advancements being made in fabrication techniques [5][6][7] and a composition of earth-abundant non-toxic elements, 8 CZTSSe is a prime candidate to replace the less sustainable, yet more efficient counterpart Cu(In,Ga)Se 2 (CIGS). For that reason, signicant effort has been made to investigate and prevent electronic losses and low open-circuit voltages (V oc ) [9][10][11] that impede cell performance and reduce the overall device efficiency 12,13 A successful attempt to reduce the voltage decit has been made by incorporation of Na into the device. The addition of Na improves efficiency by increasing grain size [14][15][16] and passivating trap states 17 that result in charge carrier recombination, thus diminishing the cell performance.…”

Band Edge Engineering for the Improvement of Open‐Circuit Voltage: Ag‐Based Selenized Cu2ZnSn(SSe)4 Surface Regulated by Lithium

“…Solar cell's V oc significantly depends on the extent of band bending at the interface of absorber/buffer. [ 4–8 ] The restricted band bending at the interface of CZTSSe/CdS results from the failure of p‐to‐n type inversion, which is caused by the extremely high concentration of p‐type Cu Zn defects near the interface [ 9 ] due to the similar ionic radius and chemical properties of Cu 2+ (0.57 Å) and Zn 2+ (0.60 Å). [ 10 ] Indeed, experiment observed that despite connecting with n‐type CdS buffer layer, CZTS side of the interface was always a p‐type characteristic without type inversion.…”