Figure - available from: Advanced Functional Materials
This content is subject to copyright. Terms and conditions apply.
Schematic illustration of a) thermal evaporation approach, b) solution approach to realize Ga‐doping into the absorber films.
Source publication
Suppressing the band tailing and nonradiative recombination caused by massive defects and defect clusters is crucial for mitigating open‐circuit voltage (Voc) deficit and improving the device performance of CZTSSe thin film solar cells. Cation substitution is one of the most commonly used strategies to address the above issues. The latest world rec...
Citations
... [7,[11][12][13] Furthermore, significant progress in the chemical passivation of grain boundaries with non-isovalent (co-)doping (Ga) has also been achieved. [14] Besides the mentioned strategies, majority carrier concentrations are crucial for the PV performance of the device. However, even though the optimal hole concentration for kesterite solar cell performance has been demonstrated to be 10 16 cm −3 , consistently reported values for high-efficiency devices have remained within the range of only 10 14 -10 15 cm −3 . ...
Kesterite photovoltaic technologies are critical for the deployment of light‐harvesting devices in buildings and products, enabling energy sustainable buildings, and households. The recent improvements in kesterite power conversion efficiencies have focused on improving solution‐based precursors by improving the material phase purity, grain quality, and grain boundaries with many extrinsic doping and alloying agents (Ag, Cd, Ge…). The reported progress for solution‐based precursors has been achieved due to a grain growth in more electronically intrinsic conditions. However, the kesterite device performance is dependent on the majority carrier density and sub‐optimal carrier concentrations of 10¹⁴–10¹⁵ cm⁻³ have been consistently reported. Increasing the majority carrier density by one order of magnitude would increase the efficiency ceiling of kesterite solar cells, making the 20% target much more realistic. In this work, LiClO4 is introduced as a highly soluble and highly thermally stable Li precursor salt which leads to optimal (>10¹⁶ cm⁻³) carrier concentration without a significant impact in other relevant optoelectronic properties. The findings presented in this work demonstrate that the interplay between Li‐doping and Ag‐alloying enables a reproducible and statistically significant improvement in the device performance leading to efficiencies up to 14.1%.
... [10][11][12] Indeed, the severe open-circuit voltage (V oc ) deficiency in CZTSSe-based photovoltaic devices is often regarded as the main culprit of this performance disparity. [13][14][15][16][17][18][19] With this in mind, reducing the V oc deficit has become an imminent scientific challenge for further advancing the kesterite-based CZTSSe photovoltaic technologies. ...
... The bottleneck for further improving the V oc and PCE of CZTSSe devices mainly lies in the absorber and its heterojunction interfaces. [13][14][15]17,18] In earlier reports, the Cu Zn acceptor defects in the CZTSSe absorber is generally regarded as the main limiting factor for the V oc loss due to the similar ionic radii and chemical properties of Cu and Zn atoms. [20][21][22][23][24] However, recent theoretical analysis and experimental studies have indicated that the presence of a large density of deep intrinsic defects like Sn Zn antisites and associated compensated defect clusters represent another pivotal source of high V oc deficit and device performance deterioration. ...
The SnZn defect passivation and heterojunction interface energetics‐modification are crucial for further improvement of open‐circuit voltage (Voc) and efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Herein, a simple but effective cation substitution strategy is reported to promote the performance of CZTSSe devices by simultaneously modifying the absorber and heterojunction interface. This is achieved by introducing the organic silicon salt C8H20O4Si into CZTSSe precursor solution as a source of silicon to partially substitute Sn with Si. Systematic studies reveal that there are two mechanisms synergistically contributing to the increase of efficiency: 1) This strategy can passivate the undesired SnZn defect in CZTSSe absorber more efficiently, leading to at least one order of magnitude lower SnZn defect density and beneficial carrier transport properties; 2) After Si incorporation, the conduction band minimum of the CZTSSe is upshifted, thus enlarging the bandgap, which ultimately optimizes the energy level structure at the CdS/CZTSSe interface and reduces interfacial energy loss by decreasing the carrier transport barrier. Consequently, the CZTSSe device with 7% Si substitution delivers a satisfactory efficiency of 13.02% owing to an increase in Voc. It is hoped the Si substitution strategy reported here can provide inspiration for developing advanced CZTSSe devices with broad application prospects.
Excellent morphology and low harmful defect states of the absorber layer are essential to fabricate the high‐performance Cu 2 ZnSn(S, Se) 4 (CZTSSe) devices. In this study, the annealing time of precursor films in air was proved to have much impact on the quality of absorber layer and the performance of devices. Appropriately extending the air‐annealing time can promote the diffusion of Na into films and O absorption on the surface of precursor films, boost the growth of crystal grain, and lessen the harmful defect density and band‐tailing states of absorber. And the appropriate extension of air‐annealing time also regulates the electrical properties of the absorber. The efficiency of CZTSSe devices is enhanced from 6.92% (1 min) to 10.1% (7 min), with the decreased V OC, Def . These enhanced properties demonstrate regulating the air‐annealing time of precursor films can be a simple and direct way for improving the performance of CZTSSe devices.
This article is protected by copyright. All rights reserved.
The Cu 2 ZnSn(S,Se) 4 (CZTSSe) material is considered a promising semiconductor material for commercial photovoltaic applications due to its high theoretical efficiency, high absorption coefficient, tunable direct bandgap, high element abundance, and low production cost.
A variable-temperature sulfoselenization process is adopted to achieve an efficiency of 11.11% for CZTSSe solar cells.
