以鈉參雜鉬電極和鈉離子佈植研究在銅銦鎵硒太陽能電池上的鈉效應

Na Effects on Na incorporation methods by Mo:Na and Na implantation

吳琬瑤

指導教授 ： 賴志煌

國立清華大學/工學院/材料科學工程學系/碩士(2012年)

摘要

世界效率的CuIn1-xGaxSe2太陽能電池是使用三階段共蒸鍍製程，以鈉玻璃(soda-lime glass, SLG)基板提供Na，效率可達20.4%[1]；在可饒式基板上，則以NaF後退火達到18.3%[2]。一直以來，Na參雜是CIGS太陽電池製程中，達到高效率的關鍵因素之一。本論文主要著重開發新穎Na參雜製程，包括：(1)以直流濺鍍Na參雜Mo靶材，得到Mo:Na薄膜做為成長CIGS的前驅層 (2)Na離子佈植於CIGS層，分別研究Na在CIGS太陽能元件上的效應。
第一部份，以Mo:Na薄膜搭配Mo薄膜的多層結構，既可做為良好的背電極，又可以藉由控制Mo:Na薄膜厚度，做不同程度的Na參雜。雖然整體提供Na含量不如由SLG擴散上來的多，但是卻更有效地表現Na效應，提升元件電性。由結果分析出，Na主要藉由鈍化V_Se缺陷，消除了由(V_Se+V_Cu)缺陷對在靠近CIGS表面形成的p+層，改善正偏壓下的光電流阻礙現象(current blocking)和提升Voc，進而提高元件效率。
第二部份，以離子佈植的方式在CIGS層參雜Na。本實驗室為少數團隊使用離子佈植研究Na效應，配合快速升溫退火修復晶格損傷，並使用拉曼光譜檢測晶格損傷和退火後的修復程度。於初步結果觀察到，在退火過程中，晶格缺陷的交互作用產生新的缺陷，影響元件電性表現。進一步藉由升溫基板佈植，可以將晶格損傷程度降到最低。配合適當退火條件，離子佈植Na，可以消除施體態缺陷，並有效提高載子濃度。

關鍵字

Cu(In,Ga)Se2 薄膜型太陽電池 ； 鈉參雜钼靶材 ； 鈉離子佈植

並列摘要

Polycrystalline CuIn1-xGaxSe2 (CIGS) solar cell with efficiency of 20.3% was reported using three-stage co-evaporation on soda-lime glass substrate. It has been known that Na diffusion from the soda-lime glass into the CIGS absorber is one of the key factors to achieve the maximum cells efficiency. In this thesis, we study to alternative Na incorporation methods, including (1) Sputtering Na doped Molybdenum film (Mo:Na) and (2) Na implantation.
In the first part, we use Mo/Mo:Na multilayer structure to serve as cell back contact and provide CIGS with Na. Na doped by Mo:Na film with increasing thickness can efficiently eliminate the current blocking, barrier for light current at forward bias, and increase the open circuit voltage than Na doped by SLG due to better compensate VSe with the help of oxygen.
In the second part, Ion implantation was applied for quantitative and spatial control of Na distribution in CIGS films. In the annealing process, the formation of donor type defects due to defects interaction decreases the carrier density of CIGS. Implantation on a heated substrate can efficiently reduce implant-induced lattice displacement and lead to an enhancement in electrical properties of device.

並列關鍵字

Cu(In,Ga)Se2 thin film solar cee ； Na doped Molybdenum target ； Na implantation

參考文獻

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