Danish researchers have investigated the impact of intrinsic pointed defects in Selenium solar cells and have concluded that these defects are not responsible for lack of tension. They prefer to believe that interfaces and extensive defects can be the cause of this known problem for this type of PV device.
Scientists led by the Swiss Federal Laboratories for Materials Science and Technology (EMPA) have investigated the origin of voltage deficiency in Selenium (SE) solar cells and have discovered that the well-known intrinsic pointed defects that characterize these PV devices are not a crucial factor that influence their performance.
“In particular, we have discovered that vacancies form different deep defect levels in the band gap, but incredible, we have also established that Selenium is tolerant for all these pointed defects,” said the corresponding author of the research, Rasmus Nielsen, said PV -Magazine. “This is an incredibly promising feature, because we have eliminated point defects as the murderers of the photovoltaic performance in Selenium Dunne film solar cells.”
With the help of time flight secondary ions mass spectroscopy (TOF sims), the Researchers initially Identified the impurities that are present in one of the best performing selenium thin film photos they built, which demonstrated a world record open circuit voltage of 0.992 V.
“As expected, we found Selenium, Tellurium and Oxygen – not a surprise how we manufacture our photovoltaic devices – but we also detected halogens, namely fluorine and chlorine,” Nielsen explained. “These impurities were unexpected, but their presence alone proves that they are murderous defects.”
The research group then collaborated with scientists from computational materials-Aron Walsh, David O. Scanlon and Seán R. Kavanagh to perform defect calculations on Trigonal Selenium (T-SE). ‘With the help of highly advanced and new approaches of first principles Density Functional Theory (DFT) defect calculations, Seán took a deep dive into both intrinsic defects in selenium that are inevitable, such as vacancies and interstitials, and the extrinsic elements that we found experimental. “
Through their analysis, the scientists discovered that the T-SE thin film crystal dimensionality plays a key role in the behavior of defects, because the self-interest-interstitials and chalcogens substitutions and “dysfavors” and heterous defects “play” because of structural flexibility.
Analysis of the effect of a series of relevant extrinsic impurities in T-SE monsters and calculating the electronic and energetic properties of these species and other likely impurities, the team discovered that most extrinsic species are inactive for doping, either because of electrical inactivity or self-compensation.
‘Of course this conclusion raises the question about what then limits the performance, “said Nielsen.” Our results indicate interfaces and extensive defects – which in principle much easier to engineer. “
Looking ahead, he said that there are “promising ways” to understand the origin of defects and to improve the related passion strategies. ‘Selenium is still in the game for tandem and within PV, “he concluded.
The findings of the investigation can be found in “Intrinsic point defect Tolerance in Selenium for indoor and tandem photovoltaic“Published in Energy and environmental science. The research team included scientists from the Technical University of Denmark and Harvard University.
Another research group presented in December 2022 A 0.30 cm2 Selenium solar cell with a world record open circuit voltage of 0.99 V. A few months later the same team showed a Selenium solar cell built with laser-ananaal with the obtaining of a record fill factor of 63.7%.
In April, another group presented the results of research aimed at understanding the opto -electronic properties and carrier dynamics of selenium solar cells. In this work they found that Mobility for carriers in Selenium are considerably promising than general thinking.
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