An applied light-beam induced current study of dye-sensitised solar cells: Photocurrent uniformity mapping and true photoactive area evaluation

Abstract

The conditions for light-beam induced current (LBIC) measurement were experimentally optimised for dye-sensitised solar cells. The impacts of too fast a laser diode modulation frequency (f) and too short a dwell time (t0) were investigated for their distortions, artefacts, and noise on the overall photocurrent map image. Optimised mapping conditions for fastest measurement were obtained at a f = 15 Hz and t0 = 900 ms. Whole device maps (nominal area 4 × 4 mm2) were obtained on devices in which fabrication defects were intentionally induced. The defects were readily resolved with the LBIC setup and conditions. The inclusion of defects had the effect of broadening the photocurrent distribution and producing a sub-optimal tail to photocurrent histograms. Photoactive areas were derived from LBIC maps and were larger than those predicted by the projected screen printing pattern by up to 25%, which has obvious implications for efficiency measurements made on nominal projected active area.