UC Irvine

Solar cells and light-emitting diodes (LEDs) are the two most beneficial optoelectronic devices to humanity with opposite functions: one converts photons into electrical power and the other one converts electrons into luminance. Remarkable advances in both applications have been made in both novel chip-level design and packaging technologies, and the continuous innovation and improvement of packaging materials and methods have played key roles in the past two decades. In this work, new packaging materials and technologies are introduced to both silicon solar cells and LEDs to enhance their performance.

The first part of this work was to develop a new silver paste with different glass frits for front-side metallization in silicon solar cells. It is shown that the replacement of micro-sized glass frits by nano-sized ones can dramatically reduce the specific contact resistivity between the resultant silver electrodes and the n-type silicon layer due to the excellent etching ability of nanopartilces on removing the anti-reflection coating (ARC). Surface modification on nano-sized glass frits by electroless plating can further improve the electrical performance by offering extra conducting channel within the insulating layers.

In the second part of this work, the influence of different die attach adhesives (DAAs) on optical and thermal performance of LED emitters was studied. The results show that with an optically clear DAA applied, the highest optical output can be achieved due to its high transparency. The optically reflective DAA also exhibit excellent optical performance, especially at low fillet coverage, which block the photons escaping from the side walls. For high power LED applications, the optically reflective DAA can achieve better thermal management than the conventional one when the bondline thickness is controlled at 7.6 micron.

The last part of this work focuses on the interaction between the LED emitters and the backside reflector, which is used to reflect the downward photons. Our results show that with both optically clear and reflective DAAs, the light output of LED emitters can be very close to that of LED emitters with backside reflectors.