Silicon Solar Cells Achieve 81.5% Fill Factor using Diffusion-Free Organic Hole Conducting Layer

• Main Authors: Kuo, Li-Jung, 郭力榕
• Other Authors: Yu, Peichen
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/rf6bwc

碩士 === 國立交通大學 === 光電工程研究所 === 108 === Achieving a high-efficiency crystalline silicon (c-Si) solar cell requires a superior carrier selective layer and a good interface passivation layer. The conventional c-Si solar cells employ a high-temperature diffusion process to fabricate a highly doped n- and p-type layer as the carrier selective layer. However, the control and equipment requirements of the diffusion process could result in cell bending, breakage and high cost, limiting the yield and throughput of c-Si solar cells. In recent years, many researchers search for diffusion-free carrier selective material to replace the complex diffusion or deposition process. In this work, we investigate three novel organic materials, DSA-ph, Ir(mppy)3, and Ir(piq)2(acac) as the carrier selective materials via a scalable blade coating technique. The HOMO level of these materials could match to the valance band of Si meaning to facilitate hole transport. We show that the contact resistance is reduced to 0.092 Ωcm2 which effectively improves carrier transfer across the p-type silicon and silver electrode. In addition, we show that the work function of organic materials could be modulated by the annealing temperature, leading to an increase of fill factor and power conversion efficiency. Moreover, the dark current voltage analysis reveal that DSA-ph and Ir(piq)2(acac) could also suppress the leakage current and improve the reliability of the device. As a result, the conventional silicon solar cells incorporating the Ir(piq)2(acac) hole-conducting layer achieve a fill factor of 81.5%, which is comparable to the Al-diffusion process. The power conversion efficiency is enhanced from 16.86% to 17.79% with a net open-circuit voltage increase by 12 mV. Although Ir(piq)2(acac) does not have an obvious passivation effect, it can be improved by incorporating an a-Si: H interface passivation layer. Preliminary results show that the minority carrier lifetime can reach 267.47s, leading to a high implied open-circuit voltage of 661 mV. Ir(piq)2(acac) is potential and novel material. The application of Ir(piq)2(acac) combining a good interface passivation layer in conventional c-Si solar cells, it would be expected to achieve high power conversion efficiency, low cost, and high reliability in the future.