電性量測應用於太陽能電池之缺陷分析

Abstract

鈣態礦電池發展至今約有15到20年的歷史，且因為製作成本相對較低再加上其效率從一開始的3.8%到2020年時達到了25.2%，所以可見其備受許多地關注，此外，科學家們透過更改電池的製作方式例如改變電池的組成結構、改變傳輸層材料、改變鈣態礦吸收層的摻雜金屬或添加物等方式以求達成更高的效率與穩定性。 不過阻礙電池效率的最大因素即為電池內部的缺陷密度因為缺陷密度會促使電子與電洞的結合進而降低電池效率，而上一段所提到的改變電池結構、改變傳輸層材料或者是電池的老化等皆會影響電池的缺陷密度，因此如何透過實驗來量測出缺陷密度，並找出和外在變因的關聯性是一個相當重要地課題。 本研究使用了單接面市售蕭特基二極體與雙接面鈣態礦電池，目的是為了量測接面與材料內部的缺陷深度與位置，本研究透過改變電壓、溫度、頻率等參數包含了DLCP、TAS、DLTS等實驗方式來對電池進行量測。在實驗設計上則採用一個實驗去量測一種變因的兩個電池的方式(例如DLTS分析變因A；TAS分析變因B)。 透過DLTS實驗發現不同時間比之下所量測出的缺陷深度與密度也會有所不同，推測在不同時間比之下可以找到不同種類之缺陷，另外有添加添加物時缺陷密度會從2.64×10^13 cm^(-3)降低到2.22×10^13 cm^(-3)進而使效率從19.33%上升到19.67%；另外透過DLCP實驗發現在沒有電洞傳輸層的電池其界面缺陷密度從9.88×10^16 cm^(-3)升高到4.36×10^17 cm^(-3)，因此效率從17.91%降低到11.72%；透過TAS發現老化的電池的缺陷密度從9.69×10^14 cm^(-3)上升到1.35×10^15 cm^(-3)，使的電池的效率從5.1%降低到約0.3%；透過CV實驗發現蕭特基二極體的載子濃度圖形，和電池的載子濃度圖形是不同的，且也說明了CV實驗之載子濃度會大於DLCP之載子濃度；最後則是透過暗室下的IV實驗檢測元件以及利用不同掃描速率的方式發現掃的速度越慢其遲滯現象越明顯。這些實驗結果和文獻比較後都是吻合的，由此便可以更加地了解外在變因對於缺陷密度之影響。

Perovskite solar cells have been developed for approximately 15-20 years , and because its production cost is low, and the beginning of the efficiency is 3.8% which improves to 25.2% in 2020, it can be seen that it raises a lot of attention. Furthermore, the scientists use a lot of methods including changing the structure of the solar cell, changing the material of the transport layers, changing the doping materials of the perovskite absorber etc. in order to achieve a higher efficiency and stability. But the most important factor that hinders the progress of the solar cells is the defect density because it promotes the recombination of holes and electrons which lower down the efficiency of the solar cells, and the factors which were mentioned in the last paragraph including changing the structure of the solar cell, changing the material of the transport layers or aging of the solar cell have influences on the defect density of the solar cells, thus how to measure the defect density through experiment and find out the relationship between defect density and the external factors is the important issue. This research uses the perovskite solar cells to measure the defect density, and it also measures Schottky diode to compare with the result of the solar cells, this research uses DLCP, TAS, DLTS etc. methods to measure, for the experimental design, we use one experiment to analyze one external factor of a group of two solar cells (e.g. DLTS on factor A, TAS on factor B). Through DLTS it was found out that under different time ratios the defect densities and defect depths are also different which maybe corresponds to different types of defect, and also find out that adding addictive can lower down defect densities from 2.64×10^13 cm^(-3) to 2.22×10^13 cm^(-3)to enhance the efficiency from 19.33% to 19.67%, furthermore from DLCP measurement it was found out that solar cells without HTL its interface defects rises from 9.88×10^16 cm^(-3) to 4.36×10^17 cm^(-3), hence the efficiency drops from 17.91% to 11.72%; from TAS measurement, it was found out that aging solar cells the densities rises from 9.69×10^14 cm^(-3) to 1.35×10^15 cm^(-3) , as a result, the efficiency drops from 5.1% to 0.3%; from CV measurement, it was found out that Schottky barrier carrier density profile is different from the solar cell’s, and it also found out that the carrier density from CV measurement is higher than the results from DLCP, finally, we use dark iv measurement to check the samples and use different scan rates to find out that the lower the scan rate, the hysteresis behavior becomes more obvious. These experiment results fit well with the research before, from this we can know more about the influences of external factors on the defect densities of solar cells.