Hole Selective Tunneling Oxide Applications with Insight into Sophisticated Characterization Techniques

Tunneling metal oxide layers combined with industrially applicable novel cleaning methods can boost the current efficiency limit, which corresponds to approximately %22 in production, of crystalline silicon (c-Si) solar cells. Within the scope of this dissertation, extremely thin tunneling layers (1-3nm) of aluminum oxide is studied in conjunction with the development of wet cleaning procedures that are feasible in production lines currently exist today. These tunneling stacks are deployed to serve as exceptional surface passivation layers due to the inherent built-in charge provided by aluminum oxide. This capability is further strengthened by the introduction of extremely well controlled wet chemical oxide which not only saturates the dangling bonds at the interface but also enables conformal growth of the aforementioned tunneling oxide layers. Therefore, the interplay between aluminum oxide thickness, which effects the passivation quality tremendously, and carrier extraction capability (contact resistance) is also taken into account by the choice of ultimate boron doping profile and the optimization of the cleaning procedure. The resulting hole collecting surface passivation stack applied on doped surfaces provided record values of recombination current densities, with highly applicable contact resistivity values, enabling one-dimensional carrier transport. This dissertation is also concerned with spatially resolved characterization methods of such industrial c-Si solar cells given the importance of defects that can exist in these large area devices. Analytical image processing algorithms pertaining to biased-photoluminescence (PL) measurements are conducted to portray 2D maps of physical significant devices parameters such as dark saturation current density and efficiency. Finally, Fourier analysis is added into the analysis of raw PL images to pick up only the defected regions of the cells

Optical Loss Analysis Of Silicon Solar Cells Using Spatial Resolved Quantum Efficiency And Reflectance Measurements

IQE data has long been a key analysis tool for c-Si cell research. Transitioning from single point measurements to spatially resolved measurements allows for the detailed analysis of quality and uniformity of the processes and materials used in cell manufacturing. This work explores how spatially resolved reflectance data can be analyzed to provide valuable information regarding the front surface texturing, rear surface properties, and ARC properties of completed solar cells

Considerations In The Extraction Of Physically Significant Parameters For Various C-Si Cell Architectures

Equivalent circuit models are often applied to experimental current-voltage (I-V) data of solar cells to quantify key features of device performance. The appropriate model to use is heavily dependent on the device architecture and the properties of each material layer. With the application of an appropriate model, physical meaning can be applied to each of the fitting parameters, to better describe the underlying device physics. This work investigates various methods in which extraction of physically significant fitting parameters can be achieved and identifies the limitations and special consideration required for specific crystalline silicon (c-Si) cell architectures. I-V characteristics of large sample sets of p-type monocrystalline and multicrystalline Al-BSF cells and p-type PERC are evaluated to provide statistical data on the ability of various electrical models to describe device performance by providing accurate, repeatable and meaningful model parameters

Effect Of Cracks On Spatially Resolved C-Si Solar Cell Parameters

Although EL images of modules with cracked cells may initially show no sign of power loss; closed cracks tend to progressively open up in the field, causing various levels of power loss revealed in the various shades of regions bound by cracks. This work investigates the effect of cracks on spatially-resolved non-encapsulated solar cell electrical parameters and to show how these relate to the observed power loss. We rely on bias-PL and EQE measurements to map out solar cell electrical parameters of cracked solar cells. The main findings were that the severity of the crack impacted solar cell parameters in different ways. Such novel approaches to looking at cracks may provide a path and classify the criticality of cracks early in the process

Impact Of Ozone-Based Cleaning On Surface Recombination With Different Passivation Materials

In this work, the impact of different ozone-based cleaning processes on the level of surface passivation achieved is determined and compared against the RCA cleaning processes. Two different passivation materials are used in this study, including hydrogenated amorphous silicon and silicon nitride plasma enhanced chemical vapor deposition (PECVD). Photoconductance measurements and calibrated photoluminescence imaging are used to evaluate the level of passivation achieved and spatial uniformity for the different cleaning processes

Crystalline Silicon Device Loss Analysis Through Spatially Resolved Quantum Efficiency Measurements

The development of ultrafast quantum efficiency measurements has made it possible to perform spatially resolved short-circuit current mapping on large area crystalline silicon solar cells. With the inclusion of concurrent diffuse reflectance measurements, detailed loss analysis is presented that identifies the impact and spatial nonuniformity of various current loss mechanisms. We measure p-type multicrystalline aluminum back surface field and p-type monocrystalline passivated emitter and rear cells, and investigate details of the spatial variation in specific device layers such as the antireflection coating, phosphorus diffused region, bulk, and rear surface. The results are compared with traditional photoluminescence imaging, and are found to provide a complementary dataset that provides a comprehensive picture of device performance. The insight provided from these techniques is intended to allow rapid feedback for quality control in manufacturing and accelerate the pace of process development in research environment

Crystalline Silicon Device Loss Analysis Through Spatially Resolved Quantum Efficiency Measurements

The development of ultrafast quantum efficiency measurements has made it possible to perform spatially resolved short-circuit current mapping on large area crystalline silicon solar cells. With the inclusion of concurrent diffuse reflectance measurements, detailed loss analysis is presented that identifies the impact and spatial nonuniformity of various current loss mechanisms. We measure p-type multicrystalline aluminum back surface field and p-type monocrystalline passivated emitter and rear cells, and investigate details of the spatial variation in specific device layers such as the antireflection coating, phosphorus diffused region, bulk, and rear surface. The results are compared with traditional photoluminescence imaging, and are found to provide a complementary dataset that provides a comprehensive picture of device performance. The insight provided from these techniques is intended to allow rapid feedback for quality control in manufacturing and accelerate the pace of process development in research environment

Optical Loss Analysis Of Silicon Solar Cells Using Spatial Resolved Quantum Efficiency And Reflectance Measurements

IQE data has long been a key analysis tool for c-Si cell research. Transitioning from single point measurements to spatially resolved measurements allows for the detailed analysis of quality and uniformity of the processes and materials used in cell manufacturing. This work explores how spatially resolved reflectance data can be analyzed to provide valuable information regarding the front surface texturing, rear surface properties, and ARC properties of completed solar cells

Effect Of Cracks On Spatially Resolved C-Si Solar Cell Parameters

Although EL images of modules with cracked cells may initially show no sign of power loss; closed cracks tend to progressively open up in the field, causing various levels of power loss revealed in the various shades of regions bound by cracks. This work investigates the effect of cracks on spatially-resolved non-encapsulated solar cell electrical parameters and to show how these relate to the observed power loss. We rely on bias-PL and EQE measurements to map out solar cell electrical parameters of cracked solar cells. The main findings were that the severity of the crack impacted solar cell parameters in different ways. Such novel approaches to looking at cracks may provide a path and classify the criticality of cracks early in the process