利用飛秒雷射掃描式退火於非真空銅銦鎵硒薄膜太陽能電池之研究

Abstract

本研究主題為利用超快雷射退火於非真空製程的銅銦鎵硒薄膜，比起傳統雷射退火，能有效改善薄膜表面的熱融熔現象。經由XRD及Raman的量測結果分析其結晶性，可發現其黃銅礦結構的(112)軸向的結晶品質及A1 mode的訊號有明顯地增強，我們推測超快雷射的強電場有效地使銅銦鎵硒的(112)方向的極性面變好。為了執行均勻大面積退火處理，我們使用超快雷射掃描式退火方式處理非真空製程的銅銦鎵硒薄膜，並經由光激發探測系統(OPOP)的量測分析，可發現其載子生命週期增長，並找到最佳的掃描速度。另外，快速雷射退火處理使原本相分離析出的銦與內部的離子再次反應，可經由PL分析缺陷活化能，發現雷射退火能有效地消除銦佔銅(InCu)、銦佔硒(InSe)硒空缺(VSe)等缺陷，缺陷的下降使得銅銦鎵硒薄膜太陽能電池元件的並聯電阻及效率提升。

In this thesis, we have successfully demonstrated that femtoscond laser annealing nonvacuum nanoparticle synthesized CIGS thin films without melt effect. The laser fluence was optimized by XRD measurement, and the quality of crystallinity in (112)-preferred orientation and the signal of A1 mode in chalcopyrite structure were significantly enhanced after fs-LA. These phenomenon can be attributed {112} is polar surface, so that the structural changes can be driven whereas electronic excitation from intensive electric field of fs laser pulses. Furthermore, the laser scanning rate was also optimized by carrier lifetimes acquired pump-probe spectroscopy. The better stoichiometry in CIGS thin films was achieved with optimized laser scanning rate owing to that the excess indium were reacting with other ions insides. It is beneficial to decrease the defect states of InSe, VSe, and InCu, which has been elaborately verified by PL spectra. These abovementioned advantages of fs-LA had greatly decreased shut leakage current and recombination centers in CIGS TFPV, resulting the significant enhancement in conversion efficiency. These results has indicated that fs-LA is a promising approach to boosting high-efficiency flexible nonvacuum CIGS TFPV.