利用量子點之螢光轉換層提升砷化鎵電池效率

Abstract

利用具螢光轉換機制之量子點將未充分利用的高能量光子轉換成太陽能電池光譜響應較佳之低能量光子。此方法克服電池在短波段的低頻譜響應與電池表面複合問題。結果顯示，量子點增加了元件在高能量光子的收集率外，同時降低其表面反射率與表面載子複合。在太陽能電池的電性不受影響之下，短路電流得到提升，進而增加了電池的效率。 本研究中，我們分析3種量子點的螢光下轉換層應用在砷化鎵電池表面的結果。實驗顯示，其短路電流有10~20%提升，電池的效率增加15~25%。進一步分析量子點在砷化鎵電池的螢光下轉換效率(量子點層吸光-放光後且在電池上產生電訊號的效率)，發現量子點在高劑量下會產生自聚集現象影響了其效率。故我們稀釋量子點的濃度，目的在減少高劑量量子點於使用下所造成自聚集現象，進而提升螢光下轉換層的效率。最佳化之量子點濃度太陽能電池相較於傳統無量子點之砷化鎵太陽能電池可提高電流18.3%，而轉換效率高達22%。 最後，量子點材料可提升任何型態之太陽能電池轉換效率，未來極具潛力成為下一世紀新穎混合型敏化太陽能電池元件。

Luminescent down-shifting layers involve the conversion from underused high-energy photon to lower energy photon where the spectral response of the solar cell is more efficient. The method overcomes the poor response and surface recombination of solar cell at short wavelength. We apply the quantum dots(QDs) as luminescent down shifting layers in single junction GaAs solar cells to improve the ultraviolet light harvesting, surface reflection, and surface carrier collection properties. As a result, the short circuit current (Jsc) is increased, then increasing the power conversion efficiency (η) without electrical properties changing. Firstly, we examined three types CdS QDs on the surface of GaAs solar cells. As a result, the Jsc increased 10~20%, then increasing the η 15~25%. By analyzing the fluorescence quantum yield (Φ) of QDs, we found that the more concentrated QDts on the surface, the less Φ become because of QDs’ self-assembly. For alleviating the self-assembly phenomenon in high dosage of QDs, we secondly demonstrates dual-layer QDs carried by flexible polydimethylsiloxane(PDMS) film. The flexible PDMS film which is fabricated by spin-coating keeps high dosage QDs to form dual layer. This method enhanced η 22%, which compares to a GaAs solar cell without QDs. Finally, QDs can apply in any kind of solar cells with increasing Jsc and η. This study shows the QDs’ potential for becoming next generation solar cell in the future.