Interdigitated Back-contact Silicon Solar Cells Research Articles

Characteristics and development of interdigital back contact solar cells

Silicon-based solar cells are an important field for the development of the photovoltaic industry. The grid electrode on the front surface of the traditional silicon solar cell causes shading loss. However, the positive and negative electrodes are placed on the back surface of the interdigitated back contact(IBC) solar cell, which causes no shading loss and improvement of photoelectric conversion efficiency. The core of the IBC silicon solar cell is the interface control, field effect control and the design of the positive and negative electrode patterns on the back. Different manufacturing processes ensure the accuracy of the grid electrode and reduce production costs. This paper systematically introduces the structure and interface characteristics and development history of IBC solar cells, and looks forward to the development trend and application prospects of IBC solar cells.

Enhancing the efficiency of silicon solar cells using ZnO nanostructures prepared by microwave-assisted hydrothermal method

In this study, zinc oxide (ZnO) nanostructures were grown on interdigitated back contact silicon solar cells (IBC-SSCs) by using the microwave-assisted hydrothermal method. The effect of these ZnO nanostructures grown by different precursor concentrations on the conversion efficiency of solar cells was investigated. The as-prepared ZnO products were analyzed by XRD, SEM, EDS, UV–vis, and PL, then were grown onto IBC-SSCs. The IBC-SSCs conversion efficiency without any ZnO nanostructure was 8.88%, and with a ZnO nanostructure, it reached 12.15%. which effectively enhances the conversion efficiency of IBC-SSCs.

Record-high solar-to-hydrogen conversion efficiency based on a monolithic all-silicon triple-junction IBC solar cell

We present a record-high solar-to-hydrogen conversion efficiency (STH) for monolithic all-silicon multi-junction solar devices. The device is based on an interdigitated back-contact silicon solar cell, in which the p- and n-regions are connected in a combination of series and parallel contacts, in order to triple the photovoltage compared to a single-junction cell. Our best device provides an open-circuit voltage of 1.99 V, larger than the water redox potential of 1.23 V plus overpotentials at the electrodes, as well as a short-circuit current density of 12.6 mA/cm2. Coupled to a sulphuric acid electrolysis system, with platinum and ruthenium dioxide electrodes, our device shows an STH of 14.5% at 1.63 V.

Metallization Method for Interdigitated Back-Contact Silicon Solar Cells Employing an Insulating Resin Layer and a Ti/Ag/Cu Metal Stack

Interdigitated back-contact (IBC) silicon (Si) solar cells are attracting increased attention due to the potential of higher efficiency that comes from eliminating front-surface shading. However, as sources of recombination loss continue to be reduced due to improved processing and use of high-quality n-type wafers, parasitic absorption in the rear metal can limit cell performance. This paper reports experimental and simulation results that identify the optical advantages of an IBC metallization method, which employs a novolac resin layer to enhance the insulation of the cell from a metal electrode comprising a sputtered Ti/Ag metal stack and plated Cu. The polymer layer can electrically decouple the metal geometry from the doping geometry and also helps to reduce the parasitic absorption at the cell rear surface by increasing the distance between the metal and Si absorber. The optical properties of the Ti/Ag stacks formed over the novolac resin were comparable to those with an Ag reflector; however, the Ti/Ag reflector offered the additional benefit of contact resistivity of < 1 mΩ·cm2 to both the n+ and p+ Si regions of the diffused IBC cells.

Improvement in IBC-silicon solar cell performance by insertion of highly doped crystalline layer at heterojunction interfaces

By inserting a thin highly doped crystalline silicon layer between the base region and amorphous silicon layer in an interdigitated back-contact (IBC) silicon solar cell, a new passivation layer is investigated. The passivation layer performance is characterized by numerical simulations. Moreover, the dependence of the output parameters of the solar cell on the additional layer parameters (doping concentration and thickness) is studied. By optimizing the additional passivation layer in terms of doping concentration and thickness, the power conversion efficiency could be improved by a factor of 2.5%, open circuit voltage is increased by 30 mV and the fill factor of the solar cell by 7.4%. The performance enhancement is achieved due to the decrease of recombination rate, a decrease in solar cell resistivity and improvement of field effect passivation at heterojunction interface. The above-mentioned results are compared with reported results of the same conventional interdigitated back-contact silicon solar cell structure. Furthermore, the effect of a-Si:H/c-Si interface defect density on IBC silicon solar cell parameters with a new passivation layer is studied. The additional passivation layer also reduces the sensitivity of output parameter of solar cell to interface defect density.

A simulation study on the electrical structure of interdigitated back-contact silicon solar cells

In this paper, a simulation for interdigitated back-contact (IBC) silicon solar cells was performed by using Silvaco TCAD ATLAS to investigate the cell’s electrical properties. The impacts of various parameters, including the depth of the front surface field(FSF), the FSF peak doping concentration, the depths of the emitter and the back surface field(BSF), the peak doping concentrations of the emitter and BSF, the base doping, and the bulk lifetime on the output characteristics like the light current-voltage curves and the internal quantum efficiency of the IBC solar cell, were investigated. The light absorption was determined by adjusting the antireflection coating and the Al thickness. The FSF must be thin and have a low doping concentration for high-efficiency IBC cells. If the conversion efficiency is to be improved, a thick emitter and a high doping concentration are needed. Because of the low resistivity of the Si substrate, the series resistance was reduced, but recombination was increased. With a high-resistivity Si substrate, the opposite trends were observed. By counter-balancing the series resistance and the recombination, we determined by simulation that the optimized resistivity for the IBC cells was 1 Ω·cm. Because all metal electrodes in the IBC cells are located on the back side, a higher minority carrier lifetime showed a higher efficiency. After the various parameters had been optimized, texturing and surface recombination were added into the simulation. The simulated IBC cells showed a short-circuit current density of 42.89 mA/cm2, an open-circuit voltage of 714.8 mV, a fill factor of 84.04%, and a conversion efficiency of 25.77%.

Development of Screen-Printed Texture-Barrier Paste for Single-Side Texturization of Interdigitated Back-Contact Silicon Solar Cell Applications.

Continuous cost reduction of silicon-based solar cells is needed to lower the process time and increase efficiency. To achieve lower costs, screen-printed texture-barrier (SPTB) paste was first developed for single-side texturization (ST) of the interdigitated back-contact (IBC) for silicon-based solar cell applications. The SPTB paste was screen-printed on silicon substrates. The SPTB paste was synthesized from intermixed silicate glass (75 wt %), a resin binder (ethyl cellulose ethoce: 20 wt %), and a dispersing agent (fatty acid: 5 wt %). The silicate glass is a necessity for contact formation during firing. A resin binder and a dispersing agent determine the rheology of the SPTB paste. In this work, by modulating various parameters, including post SPTB firing, alkali texturing, and removal of the SPTB, the ST of IBC silicon solar cells was achieved. Since the advantages of the SPTB paste include low toxicity and prompt formation of the texture-barrier, SPTB is potentially suited for simple fabrication at low-cost for solar cell applications. The cost of the SPTB is around $100/kg which is lower than the SiH4/NH3 gas ambient used in plasma-enhanced chemical vapor deposition (PECVD). Thus, the expensive Si3N4 film deposited by PECVD using SiH4 and NH3 gas ambient for silicon solar cells can be replaced by this SPTB.

Simple power-loss analysis method for high-efficiency Interdigitated Back Contact (IBC) silicon solar cells

A simple analytical method is presented to perform a power-loss analysis of high-efficiency silicon Interdigitated Back Contact (IBC) solar cells. The method assumes one-dimensional current flows for both minority and majority carriers, as well as a constant gradient (or linear profile) of minority carrier concentration from the front to the back of the solar cell. The power-loss analysis method is applied to a real IBC silicon solar cell with a conversion efficiency of 23.3%.

Screen-Printed Aluminum-Alloyed $\hbox{P}^{+}$ Emitter on High-Efficiency N-Type Interdigitated Back-Contact Silicon Solar Cells

We demonstrate the use of industrial-orientated screen-printed aluminum-alloyed emitter for high-efficiency n-type interdigitated back-contact silicon solar cells. Different cell designs with various pitch sizes and emitter fractions have been studied. With an improved front surface field (FSF), short-circuit current densities up to 40 can be obtained. By combining the best cell design and the improved FSF, a high conversion efficiency of 19.1% with Czochralski n-type material has been achieved.