Multi crystalline silicon thin films grown directly on low cost soda-lime glass substrates

Abstract

Liquid phase crystallization of silicon is a promising technology platform to grow multi crystalline silicon thin films on foreign substrates. For solar cell application it has already been demonstrated that open circuit voltages of up to 661 mV [1] and efficiencies of up to 15.9 % [2] can be achieved on a silicon layer of a few microns only. However, while the quality of the material has been continuously improved, the cost factor of the utilized substrate has been given little attention. The present work focuses on the technology transfer from technical glass substrates to low cost soda-lime glass substrates to become more attractive for commercial applications. We demonstrate first liquid phase crystallized silicon layer on soda-lime glass substrate and show that the layer adhesion by the more than twice as large expansion coefficient of soda lime glasses compared to the established technical glasses has a significant influence on various processing options and countermeasures to overcome adhesion issues have to be considered. Furthermore, we investigate the electrical performance of the resulting absorber material for silicon thin film solar cells and report our first results on the electrical performance in terms of open circuit voltages, Hall mobility's and effective minority carrier lifetimes.

Multicrystalline, Highly Oriented Thick‐Film Silicon from Reduction of Soda‐Lime Glass

“…The resulting compressive stress value of −500.0(2) MPa is lower than the range of 580 to 850 MPa reported for an LPC-silicon seed layer on Borosilicate glass. [35] This is surprising in view of the much larger thermal expansion coefficient of soda-lime versus Borosilicate glass [18] and the corresponding larger thermal stress to be expected for CSS silicon. Obviously, CSS silicon is less affected by extended lattice defects, such as dislocations, dislocation networks, and grain boundaries, which are considered as the origin of intrinsic stress in LPC silicon.…”

“…Correspondingly, LPC on soda‐lime glass for photovoltaics (PV) was recently reported, however, with a considerably lower PV efficiency of 4.3%. [ 18 ] Additionally, occasional spalling of 6 to 12 µm thick silicon layers was observed after a few days with LPC silicon on soda‐lime glass substrates. Moreover, Si layers of 12 µm in thickness, which is favored for solar‐cell performance, generally peeled off from the triple‐stack‐coated soda‐lime glass substrate after one day at the latest.…”

Toward High Solar Cell Efficiency with Low Material Usage: 15% Efficiency with 14 μm Polycrystalline Silicon on Glass

“…The possible transfer of LPC‐Si technology to low‐cost, soda lime glass substrates was recently demonstrated on test cell structures with V OC up to 580 mV . High passivation quality, thermal compatibility, adhesion, and blocking of impurities by the SiO x /SiN x /SiO x N y layers between silicon and glass (Figure ) are key to the adoption of LPC‐Si to new substrates . Alternative HJ‐based photolithography‐free contacting schemes have also been shown previously …”

“…Finally, the low deposition temperatures of heterojunction contact layers (≤200 °C) are well below the maximum temperature allowed by glass (e.g., 1000 °C for alumoborosilicate glass and 600 °C for soda lime glass) and avoid any high‐temperature step after absorber preparation. The possible transfer of LPC‐Si technology to low‐cost, soda lime glass substrates was recently demonstrated on test cell structures with V OC up to 580 mV . High passivation quality, thermal compatibility, adhesion, and blocking of impurities by the SiO x /SiN x /SiO x N y layers between silicon and glass (Figure ) are key to the adoption of LPC‐Si to new substrates .…”

Crystallization of Amorphous Silicon via Excimer Laser Annealing and Evaluation of Its Passivation Properties

“…However, additional research is required to reduce the manufacturing cost and material non-uniformity of the ELA process. This process is also unable to completely crystallize an a-Si layer with a thickness exceeding 50 nm due to its shorter optical penetration depth [17,18]. This paper provides insights into the problems that need to be addressed to ensure that ELA can be effectively and cost-effectively applied on the industrial scale.…”