Large-area p-type HIP-MWT silicon solar cells with screen printed contacts exceeding 20% efficiency

physica status solidi (RRL) - Rapid Research Letters (Impact Factor: 2.34). 08/2011; 5:286-8. DOI: 10.1002/pssr.201105311

ABSTRACT The MWT-PERC (metal wrap through passivated emitter and rear cell) concept introduced in 2006 [1, 2] combines the advantages of surface passivation [3] and the metal wrap through approach [4], resulting in an increased conversion efficiency. However, due to the required structuring of the emitter on the rear side, the process sequence is rather complex. Our simplified structure for passivated MWT solar cells, called HIP-MWT (high-performance metal wrap through), maintains the gain in efficiency while reducing the process complexity to a minimum. The simplified structure omits the formation of an emitter region on the rear surface. Therefore no structuring steps are required. Within this work, we present solar cells based on the simplified HIP-MWT structure and non-simplified MWT-PERC reference cells. The cells of both concepts are processed in parallel to enable a direct comparison.


Available from: Daniel Biro, May 30, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To overcome limitations in efficiency originating from the front side of a crystalline silicon solar cell, the concept of the selective emitter has been investigated in recent years. Several approaches have been presented and tested for their industrial feasibility. Although almost all concepts are able to achieve a gain in conversion efficiency, not all technologies are realizable due to process complexity and possible major modifications necessary for retrofitting existing production lines. This motivates a simple process flow for the fabrication of a selective emitter structure. Laser Doping from phosphorous silicate glass (PSG) is a cost attractive approach, as only one additional processing step is required for selective emitter formation and no consumables are used. In this work solar cells on both mono-and multicrystalline silicon with selective emitter have been fabricated. A beam splitter in conjunction with a high power laser system has been used to allow for high throughput processing with 10 parallel laser beams. Solar cell parameters are shown and discussed. To investigate possible hot spots under reverse bias conditions of the shallow emitter, Dark Lock-In Thermography (DLIT) measurements have been conducted and reveal no hot-spots.
  • [Show abstract] [Hide abstract]
    ABSTRACT: In back-contact solar cells, both external polarities are located at the back surface of the device, which allows for higher photocurrent generation on cell level and reduced series resistance on module level, leading to higher energy conversion efficiencies compared to conventional solar cells and modules. However, the majority charge carriers, which are generated near the back emitter, have to flow laterally e.g. through the base in order to reach the external majority carrier contact. In the present work, we analyse the lateral series resistance by means of measurement and simulation for high-performance metal wrap through (HIP-MWT) solar cells. We compare theoretical models and experimental methods to extract the effective series resistance from simulated and measured current–voltage characteristics and show that lateral voltage variations significantly increase the local recombination current. If the width of the gap between the external majority carrier contacts is reduced from the typical value of 3.5 mm to ideally 0 mm, we expect an increase of the energy conversion efficiency of approximately 0.1%abs. for cells with three continuous rear emitter contacts on 125 mm×125 mm large silicon wafers. In a simulation study, the bulk doping concentration NA and the bulk lifetime are varied yielding an optimal base resistivity of 0.6 Ω cm–1.5 Ω cm for HIP-MWT solar cells based on Czochralski-grown silicon in the degraded state of the boron–oxygen defect and an optimal resistivity of less than 1.0 Ω cm for the case of bulk lifetimes larger than ~300 µs.
    Solar Energy Materials and Solar Cells 05/2014; 124:24–30. DOI:10.1016/j.solmat.2014.01.032 · 5.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The photovoltaic (PV) market is experiencing vigorous growth, whereas prices are dropping rapidly. This growth has in large part been possible through public support, deserved for its promise to produce electricity at a low cost to the environment. It is therefore important to monitor and minimize environmental impacts associated with PV technologies. In this work, we forecast the environmental performance of crystalline silicon technologies in 2020, the year in which electricity from PV is anticipated to be competitive with wholesale electricity costs all across Europe. Our forecasts are based on technological scenario development and a prospective life cycle assessment with a thorough uncertainty and sensitivity analysis. We estimate that the energy payback time at an in-plane irradiation of 1700 kWh/(m2 year) of crystalline silicon modules can be reduced to below 0.5 years by 2020, which is less than half of the current energy payback time. Copyright © 2013 John Wiley & Sons, Ltd.
    Progress in Photovoltaics Research and Applications 11/2014; 22(11). DOI:10.1002/pip.2363 · 9.70 Impact Factor