Resistivity and lifetime variation along commercially grown Ga‐ and B‐Doped Czochralski Si ingots and its effect on light‐induced degradation and performance of solar cells

Abstract

AbstractA systematic study of the variation in resistivity and lifetime on cell performance, before and after light‐induced degradation (LID), was performed along ∼900‐mm‐long commercially grown B‐ and Ga‐doped Czochralski (Cz) ingots. Manufacturable screen‐printed solar cells were fabricated and analyzed from different locations on the ingots. Despite the large variation in resistivity (0·57–2·5 Ω cm) and lifetime (100–1000 µ s) in the Ga‐doped Cz ingot, the efficiency variation was found to be ≤ 0·5% with an average efficiency of ∼17·1%. No LID was observed in these cells. In contrast to the Ga‐doped ingot, the B‐doped ingot showed a relatively tight resistivity range (0·87–1·22 Ω cm), resulting in smaller spread in lifetime (60–400 µ s) and efficiency (16·5–16·7%) along the ingot. However, the LID reduced the efficiency of these B‐doped cells by about 1·1% absolute. Additionally, the use of thinner substrate and higher resistivity (4·3 Ω cm) B‐doped Cz was found to reduce the LID significantly, resulting in an efficiency reduction of 0·5–0·6%, as opposed to >1·0% in ∼1 Ω cm ∼17% efficient screen‐printed cells. As a result, Ga‐doped Cz cells gave 1·5 and 0·7% higher stabilized efficiency relative to 1 and 4·3 Ω cm B‐doped Cz Si cells, respectively. Copyright © 2005 John Wiley & Sons, Ltd.