Preparation and Characterization of Copper Indium Diselenide Thin Films

本研究藉由將含有銅銦合金之前驅物硒化而合成銅銦硒(CuInSe2)薄膜。含有銅銦(CuIn)及二銅銦(Cu2In)之合金奈米粒子經由硼氫化鈉(NaBH4)化學還原法在乙二醇中製備。生成之奈米粒子尺寸約在40至60奈米間。在硒化中，銅銦硒(CuInSe2)相在250℃時即開始形成。在較高之溫度時，因為銅硒(Cu-Se)化合物之存在而使薄膜中粒子之晶粒明顯成長。含有大晶粒之單相銅銦硒(CuInSe2)薄膜在550℃生成。黃銅礦結構之銅銦硒(CuInSe2)之生成藉由拉曼光譜分析而證實。然而，緻密化之薄膜並未被觀察到。 本研究第二部分為使用硼氫化鈉(NaBH4)作為還原劑及水作為溶劑，經由化學還原法製備由銅銦合金及銦組成之奈米粉體。在硒化時，銅銦硒和中間產物氧化銦(In2O3)、硒化銅(CuSe)及硒化二銅(Cu2Se)共存。薄膜中之晶粒尺寸因為銅硒(Cu-Se)相之存在而明顯增加。當硒化溫度增加至550℃時，帶有2微米尺寸晶粒之緻密銅銦硒(CuInSe2)薄膜生成。拉曼光譜分析及Rietveld精算方法證實純黃銅礦相銅銦硒(CuInSe2)之生成。藉由紫外光-可見光-近紅外光光譜分析測得銅銦硒(CuInSe2)薄膜之能隙為0.97 eV。掠射X光繞射驗證銅銦硒(CuInSe2)完整生成於薄膜中。經由此研究證實，使用合金奈米粒子在塗佈製程上為一製備銅銦硒(CuInSe2)薄膜之可能方法。此銅銦硒(CuInSe2)薄膜太陽能電池之光電轉換效率在AM 1.5G照光之下為1.47%。CuInSe2 thin films were synthesized via selenizing the Cu-In alloys-containing precursors. The alloy nanoparticles with CuIn and Cu2In were obtained via the NaBH4-assisted chemical reduction method in ethylene glycol. The nanoparticles with a size around 40-60 nm were formed. On selenization, CuInSe2 phase started to be formed at as low as 250℃. The significant grain growth of the particles was observed in the thin films selenized at elevated temperatures because of the presence of Cu-Se compounds. The monophasic CuInSe2 thin film with large grains was formed at 550℃. The formation of CuInSe2 with a chalcopyrite structure was confirmed via Raman spectroscopy. However, densified thin films were not observed. In the second part of the study, the nanopowders consisting of Cu-In alloys and In were synthesized via the chemical reduction method using NaBH4 as the reductant and water as the solvent. On selenization, CuInSe2 was found to coexist with the intermediate compounds of In2O3, CuSe, and Cu2Se. The sizes of the grains in the thin films were significantly increased because of the existence of Cu-Se phases. When the selenization temperature was raised to 550℃, the densified CuInSe2 films with a grain size of about 2 um were formed. The Raman spectroscopy and the Rietveld refinement method confirmed the formation of pure chalcopyrite phase of CuInSe2. The band gap of the CuInSe2 thin film was measured to be 0.97 eV via the UV-visible-NIR spectroscopy. The formation of CuInSe2 throughout the thin film was verified via grazing incident X-ray diffraction. Using the alloy nanoparticles for the coating process was demonstrated to be a potential way for preparing the CuInSe2 thin films. The CuInSe2 thin-film solar cells exhibited a photovoltaic conversion efficiency of 1.47% under AM 1.5G illumination