Fabrication of monolithic photovoltaic arrays on crystalline silicon by wafer bonding and deep etching techniques

Abstract

In this work, a novel technology to fabricate small ($ 1 cm 2 ) c-Si photovoltaic minimodules is shown. This technology combines two main bulk micro-machining techniques: fusion (or adhesive) bonding and anisotropic etching of silicon. Due to the fact that the photovoltaic cells are fabricated in the same wafer, it is mandatory to etch the whole substrate to ensure electrical isolation. Once the individual cells are bulk-isolated they can be connected in series so as to scale up the output voltage of the mini-array. A handling wafer is required to provide mechanical stability to the device wafer. Adhesive and fusion bonding are used to join the handling and the device wafer. First electrical results, under standard Air Mass 1Á5 (AM 1Á5) solar spectrum light (100 mW/cm 2 ), using a 9-cell series connected mini-module fabricated by fusion bonding, leads to a total open-circuit voltage of 4Á11 V, a short-circuit current of 2Á45 mA, and a maximum delivered power of 3Á8 mW for each mini-module (1Á4 cm 2 ). A 16-cell series-connected mini-module fabricated by adhesive bonding and wire bonding, yields an open-circuit voltage of 7Á45 V, a short-circuit current of 390 A, and maximum delivered power of 1Á8 mW, with 1Á1 cm 2 of mini-module area.

Monolithic interconnected modules (MIM) for high irradiance photovoltaic energy conversion: A comprehensive review

“…In 2003, Peters et al [35] presented efficiencies of 11% for MIM devices on SOI substrates using the aforementioned groove-like isolation. In 2005, using a similar design (Figure 2-e), Bermejo [36,37] and Hammud [38] presented Si MIMs with efficiencies of 4% and 10.5%, respectively.…”

c-Si photovoltaic arrays

“…PECVD silicon oxide is the deposited, contact windows opened and finally metal deposited and patterned. The bonding of the several devices in series is performed by wire bonding [5]. (Figure 1(c)) The advantage of silicon wafer fusion bonding is that this technique is easy to implement and has a good yield withstanding the high temperatures required by the fabrication process.…”

Discharging-phototransistor-integrated high-voltage Si photovoltaic cells for fast driving demonstration of an electrostatic MEMS actuator by wavelength modulation

“…Another method is the series connection of PV cells. [24][25][26][27][28][29][30] In contrast to charge pumping, this method does not require an extra area for either a charge pump circuit or compensation. Applications for a microdevice often require a small device, so the series connection method is preferable.…”

“…Because this technology is based on standard CMOS technologies, it ensures high reliability and quality of the cells. In addition, unlike conventional mesa-isolated PV cell arrays, [27][28][29][30] it does not require modifications of a standard CMOS process. Therefore, it is more acceptable for foundries than the conventional ones.…”