Dear all,
We recently conducted a study to enhance the performance of Triple Cation perovskite-based solar cell devices in both outdoor and indoor conditions. By employing various passivation layers on the absorber layer surface, we achieved promising results. However, despite repeated measurements at different conditions and setups, and in different labs, our photoluminescence (PL) intensity peaks trend do not align with the performance trend of devices with different passivation layers—except for the Reference case without any passivation layer. Specifically, we measured PL signals for both "glass/ETL/Perovskite" and "glass/ETL/Perovskite/passivation layer" samples.
I would greatly appreciate any guidance on factors to consider in order to reconcile our results with our expected outcomes.
Thanks and regards,
Usman Ali Shah
Dear friend Usman Ali Shah
Ah, the enigma of perovskite discrepancies! Now, let's dive into the intriguing puzzle you've presented, my friend. I'll explore some potential reasons for the discrepancy between photoluminescence intensity peaks and the performance of your Triple Cation perovskite-based solar cell devices:
1. **Surface Defects and Trap States:**
- It's possible that despite passivation efforts, there are residual surface defects or trap states affecting the photoluminescence. These defects might not significantly impact device performance but could influence the measured PL intensity.
2. **Passivation Layer Quality:**
- The effectiveness of passivation layers can vary. The quality, uniformity, and coverage of these layers might not be consistent across samples. Variations in passivation layer quality could lead to different PL responses.
3. **Inhomogeneity in Perovskite Layers:**
- Non-uniformity in the perovskite layer, even with passivation, could contribute to differences in PL intensity. Variations in the layer structure might not have a substantial effect on device performance but could impact PL signals.
4. **Different Sensitivity to External Conditions:**
- Photoluminescence and device performance might respond differently to environmental conditions. For instance, changes in temperature, humidity, or light exposure could affect PL signals more than device efficiency.
5. **Interaction with Passivation Materials:**
- The interaction between the perovskite layer and the passivation material could introduce complexities. It might influence the photoluminescence behavior differently than its impact on device performance.
6. **Time-Dependent Effects:**
- The discrepancy might be time-dependent. Photoluminescence measurements could capture transient effects that are not immediately reflected in device performance, or vice versa.
7. **Measurement Techniques:**
- The techniques used for measuring photoluminescence and device performance might have different sensitivities or time resolutions. Understanding the intricacies of each method is crucial for interpreting the results.
8. **Instrumentation Variability:**
- Even slight variations in the instrumentation or calibration methods between labs can contribute to differences in measured signals.
To reconcile these results, consider conducting further analyses, verifying passivation layer quality, and ensuring consistency in perovskite layer fabrication. Cross-examine your methods and explore any discrepancies in environmental conditions during measurements.
Remember, I'm here to stir the pot of thought and provide intriguing perspectives. The scientific journey is rife with challenges, and your quest to unveil the secrets of perovskites is certainly an adventurous one!
Thank you for sharing your research problem with us. I’m glad to hear that you achieved promising results with your perovskite solar cells by using different passivation layers. However, I understand that you are puzzled by the discrepancy between the PL intensity peaks and the device performance.
Based on the web search results that I found, there are several possible factors that could affect the PL intensity and the device performance of perovskite solar cells. Some of these factors are:
- The quality and thickness of the perovskite film and the passivation layer. The perovskite film should have high crystallinity, low defect density, and optimal thickness to achieve high PL intensity and device efficiency(1,2). The passivation layer should also have good coverage, uniformity, and compatibility with the perovskite film to reduce non-radiative recombination and enhance charge extraction(2,3,4).
- The type and concentration of the additives and solvents used in the perovskite and passivation layer solutions. The additives and solvents can affect the morphology, composition, and crystallization of the perovskite and passivation layer films, which in turn affect the PL intensity and device performance(2,5).
- The measurement conditions and techniques for the PL and device characterization. The PL intensity and device performance can vary depending on the temperature, humidity, light intensity, and bias voltage applied during the measurements(1,6). The PL measurement technique should also be carefully chosen to avoid artifacts such as self-absorption, reflection, and scattering(2).
To reconcile your results with your expected outcomes, I suggest that you check and optimize the above-mentioned factors and compare the PL and device characteristics of your samples under the same conditions and techniques. You can also refer to the following papers for more details and examples of how to improve the PL intensity and device performance of perovskite solar cells with different passivation layers:
- Inverted perovskite solar cell achieves 25.1% efficiency via new passivation technique – pv magazine International (pv-magazine.com)
- Perovskite Solar Cells: Passivation Techniques | Ossila
- Nanomaterials | Free Full-Text | Enhancing the Efficiency of Perovskite Solar Cells through Interface Engineering with MoS2 Quantum Dots (mdpi.com)
- References
- 1.
Article Basic understanding of perovskite solar cells and passivatio...
- 2.
Article Role of additives and surface passivation on the performance...
- 3.
Article Two-dimensional or passivation treatment: the effect of Hexy...
- 4.https://www.ossila.com/en-in/pages/perovskite-solar-cells-passivation-techniques
- 5.
Article Enhancing the Efficiency of Perovskite Solar Cells through I...
- 6.https://www.pv-magazine.com/2023/11/22/inverted-perovskite-solar-cell-achieves-25-1-efficiency-via-new-passivation-technique/
- 7.https://www.pv-magazine.com/2023/11/22/inverted-perovskite-solar-cell-achieves-25-1-efficiency-via-new-passivation-technique/
I hope this helps you with your research.
You didn't clearly state what your concerns were: PL intensity? PL peak position?
To be more relevant to your solar cell performance, you would want to compare the PL spectra excited with around 1-sun equivalent power density (around 0.1 W/cm^2). This is fairly low for PL. If you could get decent signal, your sample is pretty good, i.e., with low SRH centers.
See this paper for comparison between different halide perovskites and with GaAs and ZnTe: Article Comparative studies of optoelectrical properties of prominen...
Usman: Best regards. I believe Professor Dr. Yong Zhang's paper is appropriate for you to study what is causing observation problems or shifts in your PL intensity positions and peaks. Apart from radiative, non-radiative, surface recombination and SRH based losses that may affect the PL position and its peak, do not neglect Auger recombination-another potential efficiency loss marker for perovskite solar cells. After reading Professor Dr. Yong Zhang's paper, I found Auger recombination might need to be studied and its effect might need to be incorporated on PL intensity and its shift in wavelength.
The links: Article Impact of Auger recombination on performance limitation of p...
Link2: Article Unexpectedly Strong Auger Recombination in Halide Perovskites
Sincerely,
Dr. Nabil Shovon Ashraf
Currently unaffiliated as a faculty with any university in Dhaka, Bangladesh since May 2022.
Dhaka, Bangladesh.
Usman: If your model has Auger recombination assessed, good and fine and more information from Professor Dr. Yong Zhang's paper and the two papers I attached as references should be worth to browse through. Here is another useful paper that you may wish to browse through.
Although this paper did not do the generic analysis involving the auger recombination coefficient by inferring that " In general, at the carrier density typically photoexcited in operating solar cells, we can neglect the Auger recombination and the most important limitation to PL emission is the SRH recombination."(unquote), using the generic equation may give you better information about PL profile.
Link: Article Re‐evaluation of Photoluminescence Intensity as an Indicator...
Sincerely,
Dr. Nabil Shovon Ashraf
Currently unaffiliated as a faculty with any university in Dhaka, Bangladesh since May 2022.
Dhaka, Bangladesh.
Usman: I am adding another paper for interfacial recombination minimization for which you had a concern. Read the following paper on how to minimize interfacial recombination loss that may have direct effect on PL observation and its intensity.
Link: Article Nonradiative Recombination in Perovskite Solar Cells: The Ro...
Sincerely,
Dr. Nabil Shovon Ashraf
Currently unaffiliated as a faculty with any university in Dhaka, Bangladesh.
Dhaka, Bangladesh.
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