Interface engineering of antimony selenide solar cells: a review on the optimization of energy band alignments

Abstract

Earth-abundant and environmentally benign antimony selenide (Sb2Se3) has emerged as a promising light-harvesting absorber for thin-film photovoltaic devices due to its high absorption coefficient, nearly ideal bandgap for photovoltaic applications, excellent long-term stability, and intrinsically benign boundaries if properly aligned on the substrate. The record power conversion efficiency (PCE) of Sb2Se3 solar cells has currently reached 9.2%, however, it is far lower than the champion efficiencies of other chalcogenide thin-film solar cells such as CdTe (22.1%) and Cu(In,Ga)Se2 (23.35%). The inferior device performance of Sb2Se3 thin-film solar cells mainly results from a large open-circuit voltage deficit, which is strongly related to the interface recombination loss. Accordingly, constructing proper band alignments between Sb2Se3 and neighboring charge extraction layers through interface engineering to reduce carrier recombination losses is one of the key strategies to achieving high-efficiency Sb2Se3 solar cells. In this review, the fundamental properties of Sb2Se3 thin films, and the recent progress made in Sb2Se3 solar cells are outlined, with a special emphasis on the optimization of energy band alignments through the applications of electron-transporting layers and hole-transporting layers. Furthermore, the potential research directions to overcome the bottlenecks of Sb2Se3 thin-film solar cell performance are also presented.

Exploring Cu-Doping for Performance Improvement in Sb2Se3 Photovoltaic Solar Cells

“…By comparing the values with the undoped films, V OC raised from 315 mV to 388 mV for the cell with Mo substrate and from 256 mV to the remarkable value of 509 mV in the case of FTO substrate. This value is among the three highest ever reported for a Sb 2 Se 3 -based solar cell [ 17 , 18 , 40 ]. The short-circuit current density, J SC, also slightly increases for the cell on the Mo substrate, from a very low 0.3 mA/cm 2 to 1.5 mA/cm 2 , while unfortunately it decreased for the cell on the FTO substrate from 25.6 mA/cm 2 to 0.3 mA/cm 2 , undermining the increase in the FF from 39.2% to 51.9%.…”

“…Starting from 2014, new deposition processes were successfully tested [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ] and, pushed to the results first achieved by the closed space sublimation (CSS) technology, producing Sb 2 Se 3 films with properly oriented ribbons [ 15 , 16 ], the efficiency of Sb 2 Se 3 -based solar cells rapidly increased from <1% up to the current 10.57% record [ 9 ]. Despite this significant improvement, there are still two main issues to be solved to enhance the efficiency of ASe-based solar cells [ 5 , 17 ]. On the one hand there is still a wide margin for improvement in the choice of materials for each layer composing the cell, not only for the optimization of bands alignment [ 17 ], but also for the minimization of the interface defect density and of the surface recombination rate, that are often reported to be very high for Sb 2 Se 3 and traditional buffers such as CdS [ 5 , 6 ].…”

“…Despite this significant improvement, there are still two main issues to be solved to enhance the efficiency of ASe-based solar cells [ 5 , 17 ]. On the one hand there is still a wide margin for improvement in the choice of materials for each layer composing the cell, not only for the optimization of bands alignment [ 17 ], but also for the minimization of the interface defect density and of the surface recombination rate, that are often reported to be very high for Sb 2 Se 3 and traditional buffers such as CdS [ 5 , 6 ]. On the other hand, even on the most efficient ASe-based cells, the reported V OC (open circuit voltage) and FF (fill factor) values are generally too low and likely limited not only by the presence of deep defects that leads to the short carrier lifetime, but also by the small built-in potential due to the very low hole density (≈10 13 cm −3 ) in undoped Sb 2 Se 3 [ 5 , 6 , 7 ].…”

24% Efficient, Simple ZnSe/Sb2Se3 Heterojunction Solar Cell: An Analysis of PV Characteristics and Defects

“…12 Intrinsic point defects such as substitution/antisite (Sb Se , Se Sb ), vacancies (V Se , V Sb ), and interstitials (Se i ), which can be donor/acceptor/amphoteric, could act as both hole and electron traps and reduce the lifespan of the minority carrier lifetime and the solar cell performance. 13 An ideal buffer layer should satisfy the fundamental criteria of having good carrier mobility, high electrical conductivity, and an appropriate energy band alignment with minimum conduction band offset (CBO). 14 In Sb 2 Se 3 TFSC, CdS is a commonly used buffer layer.…”

“…The dangling bonds at grain boundaries act as recombination centers in a 3D crystal structure . Intrinsic point defects such as substitution/antisite (Sb Se , Se Sb ), vacancies (V Se , V Sb ), and interstitials (Se i ), which can be donor/acceptor/amphoteric, could act as both hole and electron traps and reduce the lifespan of the minority carrier lifetime and the solar cell performance …”