Charge transport materials for mesoscopic perovskite solar cells

Single-Crystal Perovskite for Solar Cell Applications

The advent of organic-inorganic hybrid metal halide perovskites has revolutionized photovoltaics, with polycrystalline thin films reaching over 26% efficiency and single-crystal perovskite solar cells (IC-PSCs) demonstrating ≈24%. However, research on single-crystal perovskites remains limited, leaving a crucial gap in optimizing solar energy conversion. Unlike polycrystalline films, which suffer from high defect densities and instability, single-crystal perovskites offer minimal defects, extended carrier lifetimes, and longer diffusion lengths, making them ideal for high-performance optoelectronics and essential for understanding perovskite material behavior. This review explores the advancements and potential of IC-PSCs, focusing on their superior efficiency, stability, and role in overcoming the limitations of polycrystalline counterparts. It covers device architecture, material composition, preparation methodologies, and recent breakthroughs, emphasizing the importance of further research to propel IC-PSCs toward commercial viability and future dominance in photovoltaic technology.

Super-Droplet-Repellent Carbon-Based Printable Perovskite Solar Cells

Despite attractive cost-effectiveness, scalability, and superior stability, carbon-based printable perovskite solar cells (CPSCs) still face moisture-induced degradation that limits their lifespan and commercial potential. Here, the moisture-preventing mechanisms of thin nanostructured super-repellent coating (advancing contact angle >167° and contact angle hysteresis 7°) integrated into CPSCs are investigated for different moisture forms (falling water droplets vs water vapor vs condensed water droplets). It is shown that unencapsulated super-repellent CPSCs have superior performance under continuous droplet impact for 12 h (rain falling experiments) compared to unencapsulated pristine (uncoated) CPSCs that degrade within seconds. Contrary to falling water droplets, where super-repellent coating serves as a shield, water vapor is found to physisorb through porous super-repellent coating (room temperature and relative humidity, RH 65% and 85%) that increase the CPSCs performance for 21% during ≈43 d similarly to pristine CPSCs. It is further shown that water condensation forms within or below the super-repellent coating (40 °C and RH 85%), followed by chemisorption and degradation of CPSCs. Because different forms of water have distinct effects on CPSC, it is suggested that future standard tests for repellent CPSCs should include rain falling and condensate formation tests. The findings will thus inspire the development of super-repellent coatings for moisture prevention.

Vanadium and tantalum doping of tin dioxide: a theoretical study

The increasing demand of efficient optoelectronic devices such as photovoltaics has created a great research interest in methods to manipulate the electronic and optical properties of all the layers of the device. Tin dioxide (SnO2), due to his charge transport capability, high stability and easy fabrication is the main electron transport layer in modern photovoltaics which have achieved a record efficiency. While the wide band gap of SnO2 makes it an effective electron transport layer, its potential for other energy applications such as photocatalysis is limited. To further improve is conductivity and reduce its bandgap, doping or co-doping with various elements has been proposed. In the present density functional theory (DFT) study, we focus on the investigation of vanadium (V) and tantalum (Ta) doped SnO2 both in the bulk and the surface. Here we focus on interstitial and substitutional doping aiming to leverage these modifications to enhance the density of states for energy application. These changes also have the potential to influence the optical properties of the material, such as absorption, and make SnO2 more versatile for photovoltaic and photocatalytic applications. The calculations show the formation of gap states near the band edges which are beneficial for the electron transition and in the case of Ta doping the lowest bandgap value is achieved. Interestingly, in the case of Ta interstitial, deep trap states are formed which depending of the application could be advantageous. Regarding the optical properties, we found that V doping significantly increases the refractive index of SnO2 while the absorption is generally improved in all the cases. Lastly, we investigate the electronic properties of the (110) surface of SnO2, and we discuss possible other applications due to surface doping. The present work highlights the importance of V and Ta doping for energy applications and sensor applications.

Recent Advances of Doped SnO2 as Electron Transport Layer for High-Performance Perovskite Solar Cells

Perovskite solar cells (PSCs) have garnered considerable attention over the past decade owing to their low cost and proven high power conversion efficiency of over 25%. In the planar heterojunction PSC structure, tin oxide was utilized as a substitute material for the TiO2 electron transport layer (ETL) owing to its similar physical properties and high mobility, which is suitable for electron mining. Nevertheless, the defects and morphology significantly changed the performance of SnO2 according to the different deposition techniques, resulting in the poor performance of PSCs. In this review, we provide a comprehensive insight into the factors that specifically influence the ETL in PSC. The properties of the SnO2 materials are briefly introduced. In particular, the general operating principles, as well as the suitability level of doping in SnO2, are elucidated along with the details of the obtained results. Subsequently, the potential for doping is evaluated from the obtained results to achieve better results in PSCs. This review aims to provide a systematic and comprehensive understanding of the effects of different types of doping on the performance of ETL SnO2 and potentially instigate further development of PSCs with an extension to SnO2-based PSCs.