N+ emitters realized using Ammonium Dihydrogen Phosphate for silicon solar cells

• Published in: Solar energy 2013-09, Vol.95, p.265-270
• Main Authors: Tang, Yehua, Zhou, Chunlan, Wang, Wenjing, Zhao, Yan, Zhou, Su, Fei, Jianming, Cao, Hongbin
• Format: Article
• Language: English
• Subjects: Ammonium Dihydrogen Phosphate; Applied sciences; Contamination; Diffusion; Direct energy conversion and energy accumulation; Dopants; Doping; Electrical engineering. Electrical power engineering; Electrical machines; Electrical power engineering; Electrical resistivity; Emitters; Energy; Exact sciences and technology; N+ emitter; Natural energy; Phosphorous diffusion; Phosphorus; Photoelectric conversion; Photovoltaic cells; Photovoltaic conversion; Regulation and control; Silicon; Silicon solar cells; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Temperature effects
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2013.04.024

•NH4H2PO4 (ADP) is used for the first time to realize N+ emitter silicon solar cells.•The doping profiles for various concentrations and temperatures are studied.•The uniformity is also studied.•The best efficiency (realized by ADP) is 17.97% (independently confirmed).•The best selective emitter silicon solar cell (realized by ADP) efficiency is 18.41%. Phosphorous diffusion is typically derived from three sources: phosphorus oxychloride (POCl3), sprayable phosphoric acid (H3PO4), and printable dopant phosphorous paste. Aside from being costly, these sources tend to be harmful and can facilitate bulk contamination. Ammonium Dihydrogen Phosphate (NH4H2PO4:ADP) can be used in the application of doping substrate for phosphorous diffusion, which is originally introduced in this paper. ADP doping, supported by the spin-on technique, has sufficient potential to mitigate the disadvantages of other phosphorous sources. The applicability and compatibility of ADP as a phosphorous doping source in the production of silicon solar cells were demonstrated in this paper. Sheet resistance mapping shows that ADP doping generated a uniform N+ emitter. The ADP solution concentration and diffusion temperature influenced the phosphorous dopant profile and sheet resistance. The adjustment of the concentration and temperature enables the control of the phosphorous dopant profile and sheet resistance. Full aluminum back-surface field silicon solar cells with an ADP-diffused N+ emitter were realized in this paper through screen-printed front and back contacts on 154.8cm2, 180μm thick, and 1.5–3Ωcm p-type Cz–Si wafers. The highest confirmed efficiency of the investigated cells was 17.97% with an open circuit voltage of 628.40mV, short circuit current density of 36.43mA/cm2, and fill factor of 78.47%. The average efficiency (10 cells) was 17.70%, which also verified the uniformity of the ADP-diffused N+ emitter. Selective emitter solar cells with the best efficiency of 18.41% were thus fabricated.