硒化鋅薄膜太陽能電池之結構與轉換效能

Abstract

近年來在科學技術的發展上，太陽能電池是各國積極投入的研究主題，由於石油能源有限，為落實永續發展，必須發展再生能源，太陽能電池即是再生能源中將太陽的光能轉換成電能的裝置。 本實驗利用硒化鋅與n型砷化鎵基板結構產生之太陽能電池效應，討論其發生之機制與現象。實驗主要分為五個部份，首先討論硒化鋅薄膜與所使用的鈦金電極之間的接觸行為及光電流產生機制，其次討論硒化鋅於砷化鎵基板、硒化鋅於n型砷化鎵基板之間，零偏壓下產生光電流的現象與機制，及太陽能電池之轉換效率。接著討論成長氯摻雜硒化鋅於n型砷化鎵基板上之樣品與將硒化鎘量子點成長於氯摻雜硒化鋅之間，基板為n型砷化鎵之樣品，並比較硒化鎘量子點應用於太陽能電池上之效能與現象。此外，於實驗中改變環境溫度由300 K至120 K之間進行電性量測，觀察元件在低溫下太陽能電池之重要參數隨溫度之變化以及電阻隨溫度之關係，其中於氯摻雜硒化鋅於n型砷化鎵基板上之樣品與氯摻雜硒化鋅薄膜-硒化鎘量子點-氯摻雜硒化鋅薄膜於n型砷化鎵樣品間皆發現金屬-絕緣體相變化之現象。 此外，因太陽能電池之光電轉換與金屬電極有關，本實驗進一步設計網狀電極，調配金屬電極面積與其透光度之比例，利用電子束微影系統以及真空熱蒸鍍的方法製作電極，使電極透光比利提升來增加元件之太陽能轉換效率。

The solar cell technology is one of the renewable energy technologies that shall be continuously developed because of limited resources of fossil fuels, resulting in energy crisis. The solar cell technology has grown rapidly over the years. Solar cell is a device that can convert the solar energy into electricity by photovoltaic effects. In this work, thin films of ZnSe/n-type GaAs are used for solar cell characterizations. This report is divided into five parts. In the first part, we study the interfacial effects between Ti and ZnSe and between Ti and Cl-doped ZnSe. In the second part, we discuss the phenomenon and mechanism of photocurrent at zero-bias and solar cell conversion efficiency between ZnSe grown on the two different substrates of GaAs and n-type GaAs. In the third part, we measure and compare the conversion efficiency among the ZnSe/n-type GaAs, Cl-doped ZnSe/n-type GaAs, and CdSe quantum dot embedded Cl-doped ZnSe/n-type GaAs. In the fourth part, we study the electrical properties and conversion efficiencies in the temperature range from 120 K to 300 K. In the last part of this report, we try to study the windowing effect of the Ti electrodes because the solar energy conversion relies on the interface of Ti/ZnSe. To solve this problem, we use an electron beam lithography and a thermal evaporation system to manufacture mesh-shaped electrodes on ZnSe surface. We observed an increase of energy conversion efficiency when windows for light exposures are opened on the Ti electrodes.