Pierre J. Verlinden

The surface texturization of solar cells: A new method using V-grooves with controllable sidewall angles

The bulk recombination mechanisms (such as the Auger recombination, for instance) that prevent the collection of photogenerated carriers are determining the present tendency of designing thinner silicon solar cells. Such an evolution requires light trapping methods in order to keep the average light path to good values. Light trapping can be obtained through surface texturization. A texturization method using a HF-HNO3 solution in an isotropic etching has been investigated. This method has allowed us to obtain a surface of periodic V-grooves with controllable sidewall angles. Beside the fact that this new texturization method of silicon may lead to new light trapping structures, it also shows a simple way to texturize polycrystalline silicon solar cells. A ray tracing program has been devised in order to calculate the average light path for rays having a long wavelength (those rays being not readily absorbed by the Si substrate) and the generated photocurrent (without recombination effects) in cells with varying surface texturization angles.

Multilevel metallization for large area point-contact solar cells

An analysis of the series resistances of different metallization schemes for large-area backside-contact (BC) solar cells is presented. The need for developing a multilevel metallization technology for such cells is demonstrated. The authors propose a new design for the metallization of BC cells that present a series resistance independent of the cell size. The particular features required for such a multilevel interconnection are studied, and a process using anodic oxidation of aluminum is presented. BC silicon solar cells of 0.64 cm/sup 2/ have been processed in this technology, resulting in 26.2% efficiencies at 10 W/cm/sup 2/ (100 suns AM1.5, 25.5 degrees C). Subsequent runs with a simplified process and a new cell design have given 27.3% efficiency cells. The cells have been soldered on alumina mounts. Results of thermal cycling are given.<<ETX>>

21.9% efficient silicon bifacial solar cells

This paper reports the efficiency of bifacial silicon solar cells and mini-modules fabricated at SunPower Corp. The best cell has AM1.5G front efficiency of 21.9% and rear efficiency of 13.9%. The mini-modules, each containing 20 bifacial cells, attain efficiency as high as the average efficiency of their individual cells. The best module has AM1.5G front efficiency of 20.66% and rear efficiency of 10.54%. Optical properties of the bifacial cells have also been measured and analyzed. The results show that bifacial cells, compared to monofacial cells, absorb less infrared light and thus they can operate at lower temperature in space.

20.8% PERC Solar Cell on 156 mm × 156 mm P-Type Multicrystalline Silicon Substrate

Passivated emitter and rear solar cells (PERC) on the p-type multicrystalline silicon substrate have become the focus of recent laboratory and industrial-based research because of its promising mass production perspective. This paper presents the most recent studies on PERC solar cells and reveals the realization of a world record efficiency of 20.8% PERC solar cell fabricated with screen printing technology on 156 mm × 156 mm multicrystalline substrates. To further increase cell efficiency, an optical loss analysis was conducted, which shows that the current loss due to the nonoptimum light trapping dominates the overall optical loss. Based on the analysis, an efficiency of 21.3% is achievable in the near future with further optimization.

Highly effective electronic passivation of silicon surfaces by atomic layer deposited hafnium oxide

This paper investigates the application of hafnium oxide (HfO2) thin films to crystalline silicon (c-Si) solar cells. Excellent passivation of both n- and p-type crystalline silicon surfaces has been achieved by the application of thin HfO2 films prepared by atomic layer deposition. Effective surface recombination velocities as low as 3.3 and 9.9 cm s−1 have been recorded with 15 nm thick films on n- and p-type 1 Ω cm c-Si, respectively. The surface passivation by HfO2 is activated at 350 °C by a forming gas anneal. Capacitance voltage measurement shows an interface state density of 3.6 × 1010 cm−2 eV−1 and a positive charge density of 5 × 1011 cm−2 on annealed p-type 1 Ω cm c-Si. X-ray diffraction unveils a positive correlation between surface recombination and crystallinity of the HfO2 and a dependence of the crystallinity on both annealing temperature and film thickness. In summary, HfO2 is demonstrated to be an excellent candidate for surface passivation of crystalline silicon solar cells.

An interdigitated back contact solar cell with high efficiency under concentrated sunlight

The authors present the design of silicon IBC cells and the fabrication technology which gives a 21% efficiency under one sun AM 1.5 (1000 W/m/sup 2/), 25.6% at 100X and 24.4% at 300X. Interdigitated back contact and point-contact silicon solar cells were fabricated and their efficiencies are compared. It is demonstrated that the technological process is able to maintain a high carrier lifetime in the device (780 mu sec).

Industrial Screen-Printed n-Type Rear-Junction Solar Cells With 20.6% Efficiency

Screen-printed high-efficiency industrial n-type rear-junction silicon solar cells were fabricated on 5-in commercial grade Cz wafers. A furnace-diffused boron emitter and a laser-doped phosphorous front-surface field were applied to produce n-type rear-junction cells with PECVD SiNx on the front and PECVD AlO x/SiNx on the back for surface passivation. All contacts were screen printed. An average efficiency of 20.33% was achieved, while the best efficiency was 20.65%. The initial results indicate that the potential for a higher FF can be achieved by improving the front pattern and optimizing the condition for metallization, enabling an even higher efficiency.

335-W World-Record p-Type Monocrystalline Module With 20.6% Efficient PERC Solar Cells

The objective of this study is to optimize module technologies to obtain the lowest price per Watt peak (

A one-dimensional model for the quantum efficiency of front-surface-field solar cells

/Wp) ratio and the maximum power output of a flat-plate module for a given number of high-efficiency solar cells. Using B-doped ptype monocrystalline Cz silicon wafers, 500 pieces of full square 156 mm × 156 mm solar cells with a passivated emitter and rear local contacts (PERC) were fabricated with an average efficiency of 20.6% by in-house measurement. The module includes half-cells for low interconnection losses, as well as a novel light-trapping scheme including light capture ribbon connected to the cells and a structured light reflective film between cells combined with an optimized large cell gap. The module using 60 pieces of the 20.6% efficient PERC solar cells has achieved a new world record, with a peak power output of 335.2 Wp in September2014, demonstrating a large cell-to-module factor, which is defined as Pmmp of module divided by the sum of cell Pmmp. The CTM factor of the champion module is greater than 1.11.

Untangling the Mysteries of Plated Metal Finger Adhesion: Understanding the Contributions From Plating Rate, Chemistry, Grid Geometry, and Sintering

Abstract A one-dimensional analytical model is proposed to calculate the photo-current generated in interdigitated back contact solar cells with a high-low junction at the front illuminated surface. The high-low junction is simulated by constant doping levels, mobilities and lifetimes. A study of the quantum efficiency of front-surface-field (FSF) solar cells is made and the computer results are compared with experimental results. A method of determining the real and the effective surface recombination velocity of FSF solar cells is proposed.