可應用於太陽能電池之奈米結晶矽量子點埋入式氧化鋅薄膜之特性研究

Abstract

目前在矽量子點太陽能電池的研究，其矽量子點皆埋入絕緣介質中，造成電荷傳導上的不易，因而侷限住整體的光電轉換效率。因此在本篇論文，我們提出利用氧化鋅來取代傳統的絕緣介質，因為它不但是半導體，易於電荷傳導外，更具備其他特性，例如擁有大的能隙、高的穿透率、好的結晶性、以及易於調控的電性等等，諸如以上優點，將奈米結晶矽量子點埋入氧化鋅材料中製作出的矽量子點太陽能電池非常有發展潛力。 首先我們以磁控濺鍍機交替沉積氧化鋅與矽的多層膜，在第一部分以快速升溫退火使矽量子點結晶，並利用來曼光譜與Ｘ光繞射圖譜分別確認奈米結晶矽量子點的形成與氧化鋅的結晶品質，並分析其光電特性。我們發現在較高的矽濺鍍功率下，矽原子擁有較高的表面移動動能，因此在沉積的過程便能自我聚集，在後續的高溫退火下，易於形成奈米結晶矽量子點，並得到較佳的氧化鋅薄膜結晶品質。第二部份改用爐管進行高溫退火使矽量子點結晶，是為了解決使用快速升溫退火所產生的部分問題。而在爐管退火後我們可以得到不錯的整流比與光響應。 最後一部分，我們就退火後薄膜產生很大的應力造成薄膜的剝離進行分析並試圖找尋解決方法。我們發現利用升溫製程可望解決退火後因應力造成薄膜彎曲的問題。

Researches of Si quantum dot (QD) thin film solar cell is fabricated by using nanocrystal silicon (nc-Si) QD embedded in the Si-based dielectric material. However the experimental results are still substantially lower than the theoretical value due to the unfavorable material characteristics of these Si-based matrices, that is, they are not electrically conductive. In this thesis, we propose to use Zinc oxide (ZnO) as the substitutable matrix material due to its many potential applications and unique features over other conventional wide band gap semiconductors such as high transparency, nice crystallinity, and easiness to control the electrical properties. Hence, ZnO is a suitable material to serve as the matrix for nano-crystalline Si thin film solar cells We deposited ZnO/Si multilayer thin films by radio-magnetron sputtering. At first part, the nc-Si QD formed after annealing by rapid thermal annealing thermal process. Then we investigated the nc-Si formation and crystalline quality of ZnO thin films by analyses of Raman spectra and XRD patterns. Optical-electrical properties of the multilayer thin films after annealing are also investigated. We observe that the sputtered Si atoms have more kinetic energy to aggregate together as Si nano-clusters under higher Si sputtering power. An obvious aggregation of the sputtered Si atoms during deposition is helpful for the formation of nc-Si and the better crystallization of the ZnO matrix in the nc-Si embedded ZnO thin films during the RTA process. At second part, we substitute RTA to furnace as our new thermal treatment equipment to solve some problems cause by RTA thermalprocess. Then, we observe good rectification ratio and better photon response after annealing by furnace. At the last part, we try to solve the film bending problem cause by the high stress interior the films after annealing. We observe film bending problem may be solved with a heated substrate during deposition.