Pulse duration impact on laser structured ZnO:Al

We demonstrate a laser structuring process for aluminum doped ZnO with a line-shaped Nd: YAG ultraviolet laser. This process yields a pyramid-like surface texture with structure depths of d = 1.3 mu m, which enhances light trapping in solar cells by diffraction of near infrared radiation. We investigate the impact of laser pulse duration from P 25 ns <= tau(P) <= 60 ns on the optical transmittance and electrical conductivity of laser structured ZnO:Al. Formation of the surface texture proceeds via capillary waves. Increasing laser pulse duration causes oxygen effusion during the melt phase, and thereby impairs charge carrier mobility of the laser structured films. [GRAPHICS] (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim a) Line-focused Nd: YAG UV laser locally melts ZnO: Al and b) induces capillary waves. c) Line-scanning forms wave structures, d) second scan after 90 rotation yields 2D pattern.