奈米結構銅銦鎵硒太陽能電池之研究

Abstract

銅銦鎵硒太陽能電池為目前效率居冠的薄膜太陽能電池。其高效率且成本低廉的特性，使得銅銦鎵硒太陽能電池被認為是取代傳統石化燃料最具潛力的太陽能電池。對於太陽能電池而言，許多利用奈米結構的抗反射特性增益太陽能電池效率的研究層出不窮，然而，由於銅銦鎵硒太陽能電池的元件本身反射率低且效率高，鮮少研究將奈米結構應用於銅銦鎵硒太陽能電池的效率增益。 本研究利用了銅銦鎵硒奈米針陣列，以及奈米晶粒量子點兩種奈米技術，在銅銦鎵硒太陽能電池上達成顯著的效率提升。銅銦鎵硒奈米針陣列為經由無蝕刻遮罩的離子研磨技術一階段製作完成；奈米晶粒量子點則為利用空氣脈衝式噴塗技術，將量子點埋入於透明導電層下方，兩種奈米結構的應用皆適用於工業量產。本研究也詳盡地探討了此兩種奈米結構增益銅銦鎵硒太陽能電池效率的物理機制，研究結果顯示，銅銦鎵硒奈米針陣列提升元件效率的機制，為銅銦鎵硒奈米針陣列在形成奈米針的過程當中，表層的銅空缺點缺陷濃度改變，進而在覆蓋緩衝層之後，改善元件電性所致；而奈米晶粒量子點則是透過螢光下轉換以及本身自聚集後造成散射此兩種機制，增益銅銦鎵硒太陽能電池的效率。 本研究提供了利用奈米結構大幅提升銅銦鎵硒太陽能電池效率的兩種途徑，且皆具有高產出以及低材料消耗的特性，能讓銅銦鎵硒太陽能電池成為未來再生能源供應的主力之一。

Cu(In,Ga)Se2 (CIGS) solar cells have the highest efficiency among all thin film Photovoltaic (PV) technologies. Due to the cost-efficiency advantage of CIGS, CIGS solar cells have been regarded as the most promising candidate for future renewable energy alternatives. For solar cells, research on anti-reflection engineering by nano-structures has been extensively produced. However, due to the low surface reflectance of CIGS solar cells, rare nano-structure application on CIGS solar cells for efficiency enhancement can be seen. This study utilizes CIGS nano-tip arrays (NTRs) and nano-crystal quantum dots (NQDs) as two nano-structure approaches for efficiency enhancement on CIGS solar cells. Significant efficiency enhancement has been achieved on CIGS solar cells by both of the two schemes. CIGS NTRs are fabricated by one-step mask-free ion-milling method, while NQDs used in this study are dispensed by pulsed-spray deposition coating a NQDs layer beneath the transparent conductive layer. Both methods are adaptable to mass-production for PV industry. In-depth scrutiny has also been proceeded into the underlying efficiency enhancement mechanisms. The results have shown that CIGS NTRs enhanced the efficiency through a raised concentration of copper vacancy at the surface of CIGS NTRs, which promotes ion diffusion while capping buffer layer onto CIGS and improves the electrical property of the CIGS solar cell; on the other hand, NQDs have enhanced CIGS solar cell by luminescence down-shifting and scattering by the NQDs self-assembled clusters. The two nano-structure schemes for efficiency enhancement of CIGS solar cell share the same benefits of high throughput and low material consumption, which gives CIGS solar cells a new path to future renewable energy solutions.