本篇論文旨在開發新式微米及奈米結構應用於銅銦鎵硒和銅鋅錫硒薄膜太陽能電池上，以期能以減薄或少量之吸收層來達到相同甚至更佳之電池效率；在首章銅銦鎵硒太陽能電池方面，本論文開發軟性模具輔助濕蝕刻法以製作不同微米結構於銅銦鎵硒薄膜上，週期性的微米圓頂和圓孔結構能夠由同一模具壓印而得，由於圓頂和圓孔結構所構成之透明導電層/空氣介面和結構本身與分別具有抗反射與引導長波長入射光進入較長光路徑之效果，故即使吸收層厚度減薄，微米圓頂之元件仍可增益元件效率達10.98%；在第二章，為了更進一步減低銅銦鎵硒吸收層厚度，本論文引入陽極氧化鋁模板結合掠角沉積法製做週期性氧化鋁開孔背向鈍化層並應用於超薄銅銦鎵硒太陽能電池，由於奈米凹槽陣列增加反應性濺鍍法沉積之銅銦鎵硒薄膜柱狀結晶成長之傾向使得底部留下間隙；為減低間隙的再復合作用，額外的低溫硒化可促進晶粒成長進而減少間隙的密度，背向鈍化層才能發揮作用；實驗結果發現約300奈米之銅銦鎵硒吸收層製作於背向鈍化之奈米凹槽陣列電極可增益元件效率達27.42%；第三章為進一步降低吸收層成本，採用銅鋅錫硒奈米柱陣列太陽能電池，由時域有限差分法模擬得知奈米柱陣列可增益載子產生電流密度達5.3%，而整體吸收層體積縮減達63%，然而由X光繞射與成分縱深分析發現銅鋅錫奈米柱陣列於硒化初始階段即盡數轉變為銅、鋅、錫之硒化物，延遲整體硒化反應至40至50分鐘，不利快速硒化製程，加上實際元件仍會形成連續吸收層薄膜與空孔開路，最佳之奈米柱元件效率為1.36%；第四章為解決銅鋅錫硒奈米柱不連續的問題，改以銅鋅錫硒奈米網為電池結構，此結構具備與銅鋅錫硒奈米柱相當甚至更佳之光捕捉效果若於二氧化矽奈米柱上之窗口層完全移除之情況下，由時域有限差分法模擬得知具二氧化矽/硫化鎘界面之銅鋅錫硒奈米網可增益載子產生電流密度達5.16%，而具二氧化矽/空氣界面之銅鋅錫硒奈米網可增益載子產生電流密度達16.34%，然而由X光繞射分析發現銅鋅錫奈米網之硒化機制與銅鋅錫奈米柱相似，至少須35分鐘以上之硒化時間；做為比較本文亦討論銅鋅錫合金於平面與奈米凹槽陣列電極上之硒化機制，由X光繞射與成分縱深分析發現奈米凹槽陣列電極可加速硒化反應，其原因在於較薄和不完整的硒化鋅結構。整體而言銅鋅錫硒奈米柱和奈米網太陽能電池仍需要透過調整前驅物結構或藉與傳統前驅物薄膜不同之硒化條件以達到最佳之元件效率。

This thesis, based on the current development of Cu(Inx,Ga1-x)Se2 (CIGSe) and Cu2ZnSnSe4 (CZTSe) thin film solar cells technologies, is focused on developing new strategies for thinning absorber layers, passivating rear electrodes, and light harvesting, to solve the critical issues of insufficient light absorption and rear surface recombination of ultra-thin CIGSe and CZTSe solar cells.
In the first part of the thesis, micro- and nanopatterned hydrogel stamps soaked in the bromine-methanol etchant were used for imprinting of CIGSe thin films. Various kinds of structures were successfully fabricated by the MACE process. The surface chemical and structural properties were analyzed by X-ray photoelectron spectroscopy and Raman spectroscopy, and the mechanisms of microstructures formation and the selenium enrichment are discussed as well. Afterwards, we focused on the characterization of optical and electrical properties of the devices based on microstructured CIGSe thin films. The CIGSe MDAs and MHAs were chosen to investigate the effects of surface morphologies and absorber thickness on the performance of devices. Finally, we have shown that the light scattering abilities of microstructured CIGSe devices are better than those of the flattened CIGSe devices, and thus their efficiencies could be maintained even the absorber thicknesses are reduced.
In the second part of the thesis, we used anodic aluminum substrates as the templates of nanoconcave arrays (NCAs) electrodes with Al2O3 rear passivation layers for CIGSe solar cells with reduced absorber thicknesses deposited by a reactive co-sputtering system. The Al2O3 passivation layers with periodic openings can be prepared on NCAs templates with a glancing angle deposition system. However, we found that the NCAs electrodes are not suitable for CIGSe thin films prepared by reactive co-sputtering system because of their poor carrier collection near the rear surface, which may be caused by the tendency of columnar grain growth resulted from the NCAs. To reduce the number additional unpassivated crevices near the rear electrodes, we conducted additional low-temperature selenization process. After the selenization process, the devices’ performance on the NCAs with Al2O3 passivation can be maintained with reduced thicknesses.
In the third part of the thesis, to further reduce the cost of absorber layers. We chose earth abundant CZTSe thin film solar cells and make them into nanorods (NRs) solar cells. Firstly, we used the finite-difference time-domain (FDTD) method to optimize the periodicity and porosity of the CZTSe NRs solar cells according to the carrier generation enhancement. A 5.3% enhanced JSC of 34.42 mA/cm2 compared with 32.69 mA/cm2 of the thin film counterpart could be generated with concentrated field intensity at the center of the CZTSe NRs. In addition, we found that the mechanism of CZTSe NRs formation inside the of pores of AAO templates turned out to be different from those on regular planar electrodes. Prolonged selenization duration should be applied for homogeneous CZTSe phase transformation.
In the final part of the thesis, to enhance the light trapping ability of the CZTSe solar cells and circumvent the problems we encountered in the NRs solar cells. We proposed the CZTSe nanomesh (NM) solar cells. The CZTSe NM structures were fabricated using NCAs electrodes with GLAD grown SiO2 NRs followed by electrodeposition of Cu-Zn-Sn precursor layers and selenization process. Likewise, from the FDTD simulation, we found that SiO2 NRs can puncture through the window layers while maintain their continuity; therefore, the enhanced light trapping effect can be realized through the CZTSe NM structure. From FDTD simulation, a 5.16% JSC enhancement can be generated from CZTSe NM structure with SiO2/CdS interface; in addition, a 16.34% JSC enhancement can be generated from CZTSe NM structure with SiO2/Air interface. Finally, we also discussed the different selenization mechanism between CZTSe NM structures and their planar counterpart.

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