Metallisation of boron-doped polysilicon layers by screen printed silver pastes

In this work, we report on hole selective passivating contacts, which consist of a SiOx tunnel layer and an in situ boron‐doped 300 nm thick p+ polysilicon layer deposited by LPCVD. Using a SiNx:H capping layer, we show an extremely low dark saturation current density J0 of 1 fA cm−2 after contact firing. At the same time, we demonstrate that commercially available and screen‐printed fire through Ag pastes are capable of contacting the p+ polysilicon layer, with minimum contact resistance ρc = 2 mΩ cm2. We do find increased interface recombination below the metal contacts of around 250 fA cm−2, which represents a considerable advance compared to conventional screen printed metallisation on diffused junctions

Inkjet- and FlexTrail-Printing with Low Silver Consumption for Silicon Heterojunction Solar Cells

Bifacial busbarless silicon heterojunction (SHJ) solar cells with an edge length of 156.8 mm are metalized using a commercially available Ag nanoparticle ink on the front side. By means of inkjet‐printing, a maximum conversion efficiency of 23.3% is achieved. The influence of the inkjet‐printed layer number per contact finger, which is varied from one to five, on cell performance is investigated in detail. Optima are found for one and two layers, which ensure both high efficiency and low silver consumption. Furthermore, a novel metallization technology, called FlexTrail‐printing, is introduced. Using the same ink as in the case of inkjet‐printing, the finger width is reduced from 75 ± 1 to 16 ± 1 μm. This results in an enhanced short‐circuit current density and, therefore, a maximum conversion efficiency of 23.7%. Only 0.3 ± 0.1 mg Ag nanoparticle ink (deposited at 25 °C substrate temperature) is consumed during FlexTrail‐printing on a large‐area wafer (area of 244.3 cm2) with a front grid of 80 fingers

Applicability of photonic sintering and autoclaving as alternative contact formation methods for silicon solar cells with passivating contacts

Photonic sintering, both with ultraviolet and near-infrared radiation, as well as thermal sintering with pressurization (autoclaving) is compared to a typical thermal curing of metal grids printed on heterojunction solar cells. For the metallization with screen printing, besides a polymer-based silver paste designed for photovoltaics, two commercially available pastes developed for the printed electronics industry have been chosen. One is optimized for autoclaving and the other for photonic sintering. With ultraviolet photonic sintering using a non-optimized process, lateral resistivities of the screen-printed contact fingers ρl of 7.6 µΩcm and contact resistivities at the metal/TCO interface ρc of 6.0-9.1 mΩcm2; are achieved. This is comparable to results reached with conventional thermal curing. Thereby, the main advantage of photonic sintering is the potential of significantly reducing the sintering time tsintering from 30 min to milliseconds. With autoclaving and near-infrared photonic sintering, lateral resistivities of 10.9 and 11.9 µΩcm are achieved, respectively