目前高效率的鈣鈦礦太陽能電池材料中皆含有一定濃度的有機鉛，但鉛為有毒性的元素，這將會限制鈣鈦礦太陽能電池在諸多國家產業化的推動，例如歐盟國家在2006年訂立的ROHS(Restriction of Hazardous Substances)，即針對各型電子電器設備中的有害成分含量加以限制，如鉛的含量不可超過0.1%。因此含鉛的鈣鈦礦太陽能電池的後續技術要如何發展以符合世界各國類似ROHS的環境規範，將會直接影響其位於太陽光電產業的競爭力。
本研究計畫中，為了克服含鉛的問題，我們評估是否可使用鉛的同族元素「錫」來代替。首先，本研究嘗試用一步驟法來合成無鉛鈣鈦礦(CsSnI3)，發現CsSnI3前驅物的溶劑會影響無鉛鈣鈦礦的結晶型態，使用二甲基亞碸(Dimethyl sulfoxide，DMSO)當作CsSnI3前驅物的溶劑可以形成我們要的無鉛鈣鈦礦吸光層的結晶形態。接著，在實驗過程中發現，Sn2+非常容易氧化成Sn4+而破壞無鉛鈣鈦礦的結構，為了減少Sn2+氧化成Sn4+的比例，本研究添加SnF2來補足Sn2+的空缺。我們也發現可以藉由添加過量的SnI2來改善CsSnI3薄膜之均勻性，增加無鉛鈣鈦礦吸光層的面積，預期添加過量的SnI2有較佳的光伏特性。
在實驗過程中，我們發現在還沒旋塗電洞傳輸材料及蒸鍍金前，將元件放置在無氧無水的環境下，其吸光能力經過一個月後可以維持93.8%。另外我們還發現電洞傳輸材料中的添加劑TBP是影響CsSnI3中Sn2+氧化成Sn4+的原因之一。
截至目前為止，我們以上述方式製作出的無鉛鈣鈦礦CsSnI3元件，在覆蓋上電洞傳輸材料及蒸鍍金後，無鉛鈣鈦礦層已經褪色至不具有吸收光的能力，以至於在進行I-V特性曲線時測不出其擁有任何的光電轉換效率。儘管本研究最後還是沒有做出有效率的無鉛鈣鈦礦太陽能電池，不過我們發現的一些實驗結果希望可以作為後續無鉛鈣鈦礦太陽能電池研究之參考。
關鍵字:無鉛鈣鈦礦太陽能電池、CsSnI3、Sn2+氧化、SnF2、SnI2、吸光層褪色。

Highly efficient CH3NH3PbI3 based perovskite solar cell contains a significant amount of toxic organic-lead which limits large-scale use world-widely. For instance, the ROHS (Restriction of Hazardous Substances) directive announced by EU has regulated hazardous ingredients like lead content should not exceed 0.1% in electronic equipment. Therefore, how to comply with environmental regulations for perovskite solar cell has become an urgent topic.
In order to overcome this problem, we try our attempt to replace notorious lead with tin in perovskite crystal. In particular, we examine the synthetic route on the structure deformation as well as photovoltaic properties of lead-free perovskite. Firstly, we try one-step method to synthesize the lead-free perovskite. We found that the solvent plays an important role on the phase formation of lead-free perovskite. As a consequence, lead-free perovskite CsSnI3 can be obtained by using DMSO as the solvent in the precursor solution.
However, Sn2+ in CsSnI3 is easily oxidized to Sn4+ that it will destroy the structure of lead-free perovskite. Therefore, we add SnF2 to fill the vacancy of Sn2+. In this part, the effect of SnF2 addition is investigated and we found excess SnI2 addition forms uniform film of lead-free perovskite and expected to have better photovoltaic properties on the lead-free perovskite solar cells.
We find that environment is the major factor of Sn2+ oxidized to Sn4+. If the lead-free perovskite sample is placed in an oxygen-free and anhydrous environment, and its absorbance can maintained 93.8% over a month. However, during the introduction of hole transport material (HTM), TBP which is a necessary additive in HTM drives Sn2+ oxidation and destroy the photovoltaic property of the resultant cell.
Unfortunately, we fail to report any photovoltaic data currently. Details of failure analysis is undergoing and technical issue of device fabrication is expected to be solved in near future.

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