Paul A. Basore

PC2D: A Circular-Reference Spreadsheet Solar Cell Device Simulator

Summary form only given. This paper presents a new silicon solar cell device simulator that models two-dimensional effects entirely within a Microsoft Excel spreadsheet, by implementing an iterative solution of cell formulas containing circular references. The easy-to-understand user interface for problem setup and evaluation makes this 2D program a natural companion to PC1D. The solution region is divided into a 20-by-20 grid of rectangular finite elements. Each spreadsheet entry represents the value of a solution variable at a node. This makes it easy to plot 1D or 2D graphs of the variables using the built-in spreadsheet graphic functions. The complex physics in the near-surface region is replaced by surface boundary conditions using a version of the conductive-boundary model recently published by Brendel. Example device simulations will be shown and explained for a selective-emitter (SE) cell, an emitter-wrap-through (EWT) cell, and an interdigitated-back-contact (IBC) cell.

Understanding Manufacturing Cost Influence on Future Trends in Silicon Photovoltaics

The value of any new photovoltaics (PV) technology depends on its anticipated performance and manufacturing cost. Computer models can be used to predict module and system performance, but there are few tools available for predicting the future manufacturing cost of PV technologies while they are still under development. This paper presents a useful approach for comparing the cost of competing silicon cell and module concepts that minimizes the extrinsic influences of location, timing, and scale. As such, it is targeted at PV specialists tasked with choosing a technology platform to develop for future production.

All-aluminum screen-printed IBC cells: Design concept

A design concept supported by numerical device modeling is presented for a p-type IBC cell with screen-printed aluminum for both contact polarities. Applying such a design to Cz silicon appears to offer cell efficiency exceeding 20%. The key enabling feature for this design is cleaving each cell into strips held together by tape. These strips are then connected electrically in series using extrusion printing after the strips are laminated to the module glass. The resulting module technology is called SPLICE, for “Screen Printed Locally Interdigitated Contact Elements”.

Economics of future growth in photovoltaics manufacturing

The past decades record of growth in the photovoltaics manufacturing industry indicates that global investment in manufacturing capacity for photovoltaic modules tends to increase in proportion to the size of the industry. The slope of this proportionality determines how fast the industry will grow in the future. Two key parameters determine this slope. One is the annual global investment in manufacturing capacity normalized to the manufacturing capacity for the previous year (capacity-normalized capital investment rate, CapIR, units

Leveraging Silicon Epitaxy to Fabricate Excellent Front Surface Regions for Thin Interdigitated Back Contact Solar Cells

/W). The other is how much capital investment is required for each watt of annual manufacturing capacity, normalized to the service life of the assets (capacity-normalized capital demand rate, CapDR, units

Economics of tandem flat plate photovoltaic modules

/W). If these two parameters remain unchanged from the values they have held for the past few years, global manufacturing capacity will peak in the next few years and then decline. However, it only takes a small improvement in CapIR to ensure future growth in photovoltaics. Any accompanying improvement in CapDR will accelerate that growth.

Crystalline silicon on glass (CSG) thin-film solar cell modules

Epitaxy can be used to fabricate doped front surface regions that enable high interdigitated back contact (IBC) silicon solar cell efficiency. One- and two-dimensional simulations show that an epitaxial layer with a constant phosphorus dopant concentration on the order of 1017 -1018 cm-3 can possess the properties of an excellent front surface region for an n-type IBC cell. With appropriate control of dopant concentration and thickness, the epitaxially grown region passivates a textured surface, and provides the lateral conductivity necessary to enable high fill factor. The combination of these two factors drives a simulated efficiency improvement above 0.3% absolute over an n-type IBC cell with a typical 200-Ω/sq phosphorus diffusion (e.g., from POCl3). Importantly, the epitaxial front surface region can occupy the entire volume of the pyramidal texture. We, therefore, propose an exemplary process sequence for device fabrication that places texture etching after epitaxial growth.

Chain link metal interconnect structure

Tandem modules, formed by stacking two PV cells, either monolithically or mechanically, can offer higher solar conversion efficiency than modules that use only one type of PV cell. Such modules necessarily cost more per unit area than either single-junction alternative, but the increased efficiency leverages area-related costs to potentially reduce system cost per watt. High-efficiency, low-cost tandems could arise if the cost of III-V cells is reduced to approach the cost of silicon cells, or if stable large-area perovskite cells are demonstrated with efficiency approaching that of todays best laboratory devices. Within the scope given by these optimistic assumptions, future costs and performance still have a substantial range of uncertainty. A probabilistic Monte Carlo model is presented that generates a large number of cost and performance scenarios based on a range of values for each input parameter. The results can be used to assign a probability, within the scope of the assumptions, that the tandem will be more cost-effective than either single-junction alternative. Four types of tandem modules are analyzed: (1) III-V on silicon, (2) III-V on thin film, (3) perovskite on silicon, and (4) perovskite on thin film. All of these tandems have a reasonable chance (>10%) of providing slightly lower cost per watt for residential systems, and the two thin-film options might also slightly benefit utility-scale systems. Achieving a substantial cost benefit is less likely. Only the perovskite on thin film tandem has a reasonable chance of reducing system cost per watt by more than 10% for residential systems, or of reducing system cost per watt by more than 5% for utility-scale systems.