Why Pulse Duration Matters in Photovoltaics

Abstract

In the manufacture of thin‐film photovoltaic (TFPV) solar panels, Q‐switched diode‐pumped solid‐state (DPSS) lasers are routinely used for “laser scribing” – the selective removal of thin‐film materials. These lasers are available at various wavelengths (266–1064nm), output powers (0.5–34W), repetition rates (up to 500KHz) and pulse durations (<10 to greater than 100ns).Developing the ideal laser scribe process – that is, one that removes only the desired material leaving the adjacent material unaffected – can be a challenge. In a non‐ideal scribe process, not only can there be leftover material, but also high ridges can form along the scribe line. Additionally, the supportive glass substrate can develop micro‐cracks that can then cause lift‐off of the thin‐film material. Because these unwanted ridges and burrs interfere with subsequent thin‐film layers, these non‐uniformities can lead to electrical shorts that reduce TFPV efficiencies and yields.This article addresses the various ways in which pulse duration affects the laser scribe process – specifically thin‐film removal thresholds, scribe quality and substrate quality. It is shown that laser systems with shorter pulse durations will generally result in a laser scribe process that has lower material removal thresholds, cleaner scribes and minimal damage to glass substrates, ultimately leading to higher yields and lower overall manufacturing costs of TFPV panels.