Improvement in Sb₂Se₃ Solar Cell Efficiency through Band Alignment Engineering at the Buffer/Absorber Interface

Abstract

Energy band alignment plays an important role in heterojunction thin-film solar cells. In this work, we report the application of ternary Cd x Zn 1−x S buffer layers in antimony selenide (Sb 2 Se 3 ) thin-film solar cells. The results of our study revealed that the Cd/Zn element ratios not only affected the optical band gap of Cd x Zn 1−x S buffers but also modified the band alignment at the junction interface. A Sb 2 Se 3 solar cell with an optimal conduction-band offset value (0.34 eV) exhibited an efficiency of 6.71%, which represents a relative 32.1% enhancement as compared to the reference CdS/Sb 2 Se 3 solar cell. The results further indicated that a "spike"-like band structure suppressed the recombination rate at the interface and hence increased the device open-circuit voltage and fill factor. Electrochemical impedance spectroscopy analysis exhibited that the Cd x Zn 1−x S/Sb 2 Se 3 solar cell had higher recombination resistance and longer carrier lifetime than the CdS/Sb 2 Se 3 device. KEYWORDS: Sb 2 Se 3 , band alignment, Cd x Zn 1−x S/Sb 2 Se 3 heterojunction, substrate configuration, electrochemical impedance spectroscopy

An effective combination reaction involved with sputtered and selenized Sb precursors for efficient Sb2Se3 thin film solar cells

“…[15] It shows that the evolutions of (221) diffraction peaks ( Figure 3c) and PCE ( Figure 3d) of the Sb 2 Se 3 thin film solar cells follow the same trend where the optimized condition could be obtained once the selenization was conducted at 400 °C for 15 min (15min-Sb 2 Se 3 ). Consistent with efficient Sb 2 Se 3 thin film devices manufactured via other deposition techniques, [16,19,23] the PCE of our devices correlates strongly with the orientation and crystallinity of the Sb 2 Se 3 absorber layer.…”

“…Interface engineering was also conducted in Sb 2 Se 3 devices as attempts have been made by introducing additional buffer layers to passivate defects at the heterojunction. [9,18,23] However, it is widely accepted that a perfected light absorber layer still plays the most important role in Sb 2 Se 3 photovoltaics.…”

Boosting VOC of antimony chalcogenide solar cells: A review on interfaces and defects

“…[51,57] For example, Cd 0.75 Zn 0.25 S-based device demonstrated higher V OC (403 mV) than CdS-based device (383 mV), which mainly attributed to its optimal CBO (0.34 eV) compared with the latter (−0.09 eV). [58] For easy reference, the energy levels for widely used ETMs, Sb 2 X 3 , HTMs, and electrodes are summarized in Figure 6. For a detailed review on the status and origin of V OC loss in antimony chalcogenide solar cells, both nonspecialists and specialists can refer to the work of Tang group.…”

Improved Open‐Circuit Voltage of Sb2Se3 Thin‐Film Solar Cells Via Interfacial Sulfur Diffusion‐Induced Gradient Bandgap Engineering

“…[ 17 ] While in case of Sb 2 Se 3 planar structure with the highest PCE (9.2%), it is more than 0.70 V. [ 15 ] Such a severe V OC deficit can be attributed to the complicated deep defects, the short carrier lifetime, the unexpected surface/interface recombination and space‐charge region (SCR) recombination. [ 18 ] To cope such issues, various strategies have been attempted, such as absorber engineering of postselenization, [ 19 ] in situ sulfurization, [ 20 ] coevaporation of Sb 2 Se 3 /Se, [ 21 ] and external doping, [ 22 ] interfaces engineering of optimizing band alignment through single/double buffer layer modification, [ 23,24 ] introducing hole transport layers like PbS quantum dots, [ 25 ] spiro‐OMeTAD, [ 26 ] and CZ‐TA. [ 27 ]…”