Santhosh Ramesh

Perovskite solar cells are one of the most promising photovoltaic technologies in the last decades. Inverted (p–i–n) cells using NiO_X as hole‐transport layer (HTL) have gained attention due to their easy fabrication methods and high stability, although they often exhibit reduced efficiencies due to non onlyoptimized energy‐level alignment. To address this issue, different approaches have been developed, such as the use of self‐assembled monolayers (SAMs) on top of the HTL. Herein, a comparative study between regular p–i–n cells and cells using Me‐PACz as an SAM on top of NiO_X is we presented. Devices with SAM exhibit enhanced open‐circuit voltage and efficiency. Temperature DC and AC characterization reveals that the incorporation of SAM reduces recombination at the interface, as seen from the comparison of the perovskite bandgap (1.6 eV) and carrier activation energy ≈1.1 and ≈1.59 eV for reference and SAM, respectively. Finally, an outdoor degradation experiment with minimodules has been conducted. The experiment spanned for more than 500 days, and results show that minimodules with SAM were less stable than those based on the reference layer structure. This is due to a severe decrease in the short‐circuit current, which could be attributed to a deterioration of the SAM spacer.

This study presents a comprehensive evaluation of Copper Indium Gallium Selenide (CIGS) solar technology, benchmarked against crystalline silicon (c-Si) PERC PV technology. Utilizing a newly developed energy yield model, we analyzed the performance of CIGS in various environmental scenarios, emphasizing its behavior in low-light conditions and under different temperature regimes. The model demonstrated high accuracy with improved error metrics of normalized mean bias error (nMBE) ~ 1% and normalized root mean square error (nRMSE) of ~ 8%–20% in simulating rack mounted setup and integrated PV systems. Key findings reveal that the CIGS technology, while slightly underperforming in integrated, low-irradiance setups, shows comparable or superior performance to c-Si PERC technology in high-irradiance and high-temperature conditions. A significant focus of the study was on the low-light performance of CIGS, where it exhibited notable voltage losses. Our research highlights the importance of reducing the diode ideality factor for enhancing CIGS power conversion efficiency, particularly In low-light conditions. These insights provide a pathway for future research and technological improvements, emphasizing defect engineering, passivation strategies to advance the understanding and application of the CIGS technology.

Understanding the behavior of mobile ions in perovskite‐based solar cells (PSCs) is crucial for improving their performance and stability, which belong to the key hurdles in advancing this technology toward commercialization. This study explores the role of mobile ions in PSCs using the comprehensive technology computer‐aided design model which is extended to simulate the frequency‐dependent capacitance (C–f) of PSCs. It is compared with equivalent circuit approaches showcasing the validity and advantages of full device modeling. By combining the simulation of full measurement procedures with C–f and J–V measurements on experimental test structures, the observed C–f characteristics can be quantitatively related to performance losses in scan‐time‐dependent J–V curves, both originating from ion diffusion. With this combined analysis, insights can be provided on the physical origin and interpretation of the different C–f plateaus caused by the displacement of ions. Finally, the C–f characteristics of PSCs under illumination and the impact of band alignment and recombination at the perovskite interface are investigated. Experimental PSCs with and without electron‐transport layer passivation are fabricated, showing a good agreement between the simulated and measured C–f and pointing toward a lower surface recombination for the passivated PSC. This study shows how drift‐diffusion modeling helps to characterize and interpret capacitance‐based data.

A multifaceted characterization approach is proposed, aiming to establish a link between nanoscale electrical properties and macroscale device characteristics. Current–voltage (I–V) measurements are combined with admittance spectroscopy (AS) and deep‐level transient spectroscopy (DLTS) for the analysis of charge‐related performance losses with time‐of‐flight secondary‐ion mass spectrometry to complete the understanding of ionic motion in the device. This is applied to the study of surface treatment in perovskite solar cells, which implements several strategies to improve band alignment, perovskite grain growth, and chemical passivation. An increase of both open‐circuit voltage (V_oc) and fill factor of respectively 90 mV and 11% is shown after surface treatment, with an absolute efficiency increase of 4%. AS measurements, coupled with a lumped elements model, rule out the impact of transport layers as the origin of the performance improvement, rather pointing toward a reduction in ionic resistance in the perovskite bulk. Analysis of the DLTS response yields an activation energy of 0.41 eV, which is likely related to the same ionic mechanism discovered with AS. Finally, both of these techniques enable to show that the surface treatment main contribution is to reduce ion‐related recombination of charge carriers.

Copper indium gallium selenide (CIGS) is a commercialized, high-efficiency thin-film photovoltaic (PV) technology. The state-of-the-art energy yield models for this technology have a significant normalized root mean square error (nRMSE) on power estimation: De Soto model—26.7%; PVsyst model—12%. In this work, we propose a physics-based electrical model for CIGS technology which can be used for system-level energy yield simulations by people across the PV value chain. The model was developed by considering models of significant electrical current pathways from literature and adapting it for the system-level simulation. We improved it further by incorporating temperature and irradiance dependence of parameters through characterisation at various operating conditions. We also devised a module level, non-destructive characterization strategy based on readily available measurement equipment to obtain the model parameters. The model was validated using the measurements from multiple commercial modules and has a significantly lower power estimationnRMSEof 1.2%.