Effects of (i)a-Si:H deposition temperature on passivation quality and performance of high-efficiency silicon heterojunction solar cells

Abstract

Excellent surface passivation induced by (i)a-Si:H is critical to achieve high-efficiency silicon heterojunction (SHJ) solar cells. In this study, we investigated the effects of (i)a-Si:H deposition temperature on passivation quality and solar cell performance. Among the deposition temperatures we investigated <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${(140\ -200^{\mathrm{o}}\mathrm{C})}$</tex> , lower temperatures seem to result in less dense (i)a-Si:H films, which hinder their surface passivation capabilities. However, with additional hydrogen plasma treatments (HPTs), those (i)a-Si:H layers exhibited significant improvements and better passivation qualities than their higher temperature counterparts. On the other hand, even though we observed the highest VOCs for cells with (i)a-Si:H deposited at the lowest temperature (140 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${{}^{\circ}\mathrm{C})}$</tex> , the related FFs are poorer as compared to their higher temperature counterparts. The optimum trade-off between VOC and FF was found with temperatures ranging from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${160^{\circ}\mathrm{C}}$</tex> to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${180^{\circ}\mathrm{C}}$</tex> , which delivered independently certified efficiencies of 23.71%. Thus our study reveals two critical requirements for optimizing the (i)a-Si:H layers in high-efficiency SHJ solar cells: (i) excellent surface passivation quality to reduce losses induced by interface recombinations and (ii) less-defective (i)a-Si:H bulk to improve the charge carrier collections.