A significant leap has been made in the field of solar energy with the introduction of a new universal passivator aimed at improving the efficiency and stability of perovskite solar cells (PSCs). Researchers have developed this innovative strategy to tackle the persistent issue of interfacial trap-assisted nonradiative recombination, which has been known to hinder the performance of perovskite-based photovoltaic technologies.
The new passivator, identified as L-valine benzyl ester p-toluenesulfonate (VBETS), has demonstrated remarkable results. Under optimal conditions, PSCs modified with VBETS achieved a power conversion efficiency (PCE) of 26.28%. This efficiency surpasses many of its peers within the growing perovskite solar technology domain and marks a pivotal step toward commercial viability.
The need for this advancement arose from inherent challenges faced by PSCs, particularly their susceptibility to ion migration and the prevalence of deep-level defects. These issues contribute to energy losses and reduced durability over time—a significant barrier to the wide adoption of this promising solar technology.
Historically, several research teams have pushed the PCE boundaries of PSCs past the 26% threshold, highlighting the technology’s potential. For example, tandem solar cells, which stack different materials to capture various parts of the solar spectrum, have achieved efficiencies as high as 34.6%. Yet, the commercial deployment of both single-junction and tandem cells remained elusive due to their limited long-term stability against environmental factors.
The innovative approach taken by the researchers revolves around the careful design of organic ammonium salts to passivate surface defects effectively. This enabling technology hinges on adjusting the number of hydrogen atoms and managing steric hindrance via molecular engineering. By employing VBETS, which efficiently neutralizes both positively and negatively charged defects on the perovskite surface, the researchers mitigated the energy loss typically experienced at the interface.
According to the authors of the study, the defect passivation effect of cations, including VBETS, is influenced significantly by the balance between the number of hydrogen atoms present and the size of the cations used. Testing revealed this balance is pivotal for enhancing the overall efficiency of these solar cells.
Beyond achieving summervetical efficiency benchmarks, the VBETS passivator also demonstrated substantial improvements concerning long-term operational stability. Under continuous light exposure conditions, VBETS-modified single-junction PSCs were able to retain about 90.8% of their initial efficiency after 4,000 hours, overshadowing control devices which only maintained around 70.9% efficiency. Such stability improvements could be pivotal for the widespread adoption of solar technologies.
Strikingly, the large-area PSC modules created using this advanced technology reported efficiencies of 21.00%, showcasing not just laboratory potential, but scaling it up to commercial dimensions presents the technology's practicality.
When combining the results from various experimental methods, the rigorous analysis pointed to significant reductions in defect density and nonradiative recombination losses within the modified PSCs. These enhancements were confirmed through diverse characterization techniques such as photoluminescence and transient photocurrent measurements.
Overall, the findings from the study stem from the need for more reliable and efficient solar technologies. The universal applicability of VBETS as a passivator for both single-junction and tandem PSCs indicates not only advances within specific laboratory settings but marks a significant breakthrough for the field of photovoltaics.
The research concludes by emphasizing the transformative impact of VBETS and its design strategy, which might guide future developments aimed at refining the efficiency and reliability of perovskite solar technology. Further explorations are necessary to fully leverage the potential of these materials and to broaden their applicability across different solar technologies.