| 摘要: | 錫鈣鈦礦太陽能電池(Tin Perovskite solar cells，簡稱TPSCs)中錫鈣鈦礦吸收層因具理想的能隙(∼1.4 eV)和較低的毒性而有巨大的前景，TPSCs之最高光電轉換效率(Power conversion efficiency, PCE)已達15%以上。但錫鈣鈦礦因Sn2+容易氧化及快速結晶，導致穩定性差及薄膜品質不佳，另外還有載子傳遞層與錫鈣鈦礦層的介面相容性不好等問題。許多學者透過在錫鈣鈦礦前驅液中加入添加劑抑制Sn2+的氧化，而對介面相容性的問題則較少研究。本研究以已發表的PDTON結構為基礎，以具有電洞傳輸能力的isopropyl-triphenylamine (i-pr-TPA)做為Acceptor，並將原先以TPA結構搭配一條親水鏈之Donor改為同樣具電洞傳輸能力的cyclopentadithiophene (CPDT)搭配兩條親水的烷基胺側鏈，合成出兩性高分子PTSN。PTSN的好處有三: 一為CPDT結構中具有電洞萃取能力之噻吩，能有效地將電洞從錫鈣鈦礦層中萃取出來。二為CPDT相較於TPA，結構中可再增加一條親水烷基胺鏈，以更好的修飾電洞傳遞層(HTL) Cu-SnCo2O4 (Cu-SCO)的表面及HOMO能階，來更加匹配錫鈣鈦礦的價帶，且路易斯鹼烷胺基可鈍化錫鈣鈦礦表面的缺陷。三為結構中同時具親、疏水基團，可增加與錫鈣鈦礦前驅液的相容性。兩個高分子(PTSN與PDTON)的熱裂解溫度皆大於200℃。UV-Vis吸收光譜顯示在相同濃度下，PTSN溶液及膜的光吸收度皆較PDTON小，可使更多光子到達錫鈣鈦礦吸光層。在Donor結構中含兩條親水鏈之高分子PTSN膜的錫鈣鈦礦前驅液接觸角較在PDTON膜上小，顯示與親水性之錫鈣鈦礦前驅液的相容性大。Cu-SCO/PTSN膜的價帶(-5.53 eV)比Cu-SCO/PDTON膜的價帶(-5.49 eV)更接近錫鈣鈦礦的價帶(-5.74 eV)，電洞在傳遞時的能量損失較少。FTIR光譜顯示PTSN+SnI2及PTSN+Cu-SCO的amine C-N stretching與thiophene C-S stretching皆比純PTSN的波數藍位移，代表胺基上氮的孤對電子與噻吩上硫的孤對電子，都能與Cu-SCO膜及錫鈣鈦礦配位未飽和之Sn2+作用。PL及TRPL數據顯示錫鈣鈦礦沉積在經PTSN修飾的Cu-SCO上的螢光強度比沉積在Cu-SCO/PDTON或Cu-SCO HTLs上弱且載子生命週期也較短，表示Cu-SCO/PTSN HTL能最有效的將錫鈣鈦礦中的電洞萃取出來。將高分子PTSN做為錫鈣鈦礦層與HTL間之介面修飾層所組裝之反式TPSCs的PCE可達9.30% (而以Cu-SCO/PDTON及Cu-SCO為HTL的元件效率分別為8.06%及7.91%)。;The absorbers of Tin Perovskite solar cells (TPSCs) have great prospects due to their ideal energy gap (∼1.4 eV) and low toxicity. The power conversion efficiency (PCE) has achieved a significantly value of 15%. However, the tin perovskite absorber is susceptible to Sn2+ oxidation and rapid crystallization, leading to problems such as poor stability, and poor film quality. Moreover, the cell may have poor interfacial compatibility between carrier transporting layer and tin perovskite layer. Lots of researches focus on adding additives to the tin perovskite precursor solution to inhibit the oxidation of Sn2+, but less studies focus on the issue of interfacial compatibility. In this study, we used a published polymer PDTON as a base, using the same isopropyl-triphenylamine (i-pr-TPA) with hole transport ability as the Acceptor. The hole-transporting moiety cyclopentadithiophene (CPDT) with two hydrophilic alkylamine side chains was used (instead of TPA on PDTON) as a donor to prepared a new bipolar polymer PTSN. There are three advantages of PTSN: First, it uses the hole-extracting thiophene in the CPDT structure to extract effectively the holes from the tin perovskite layer. The second is that compared to TPA, CPDT has two hydrophilic alkylamine chain can better modify the surface and HOMO energy of the hole transport layer (HTL) Cu-SnCo2O4 (Cu-SCO) to match better the valence band of the tin perovskite and the Lewis base amine group can passivate the defects of the tin perovskite film. The third is that PTSN has both hydrophilic and hydrophobic groups, which can increase the affinity between the tin perovskite precursor and PTSN. The thermal decomposition temperatures of both polymers are greater than 200°C. UV-Vis absorption spectra show that at the same concentration, the light absorption of the PTSN solution and film is smaller than those of PDTON, allowing more photons to reach the tin perovskite absorber. Contact angle of the tin perovskite precursor solution on PTSN film is smaller than that on the PDTON film, indicating that the compatibility with tin perovskite precursor solution is better. Moreover, the valence band edge (-5.53) of the Cu-SCO/PTSN film better matched with the valence band (-5.74 eV) of the tin perovskite than that (-5.49) of Cu-SCO/PDTON film therefore the energy loss of hole transporting is less. FTIR spectra show that the C-N stretching of amine and C-S stretching of thiophene of PTSN+SnI2 and PTSN+Cu-SCO both blue-shifted compared to pure PTSN, indicating that the lone pairs of nitrogen on the amine group and sulfur on thiophene could interact with the coordinated unsaturated Sn2+ of Cu-SCO film and tin perovskite surface. PL and TRPL data show that the fluorescence intensity of tin perovskite deposited on PTSN-modified Cu-SCO is weaker than that deposited on Cu-SCO/PDTON and Cu-SCO HTLs, and the carrier lifetime is also shorter, indicating that Cu- SCO/PTSN HTL can most effectively extract the holes from tin perovskite. The PCE of inverted TPSCs using polymer PTSN as the interface modification layer can reach 9.30% (compared to 8.06% for using PDTON as a interface modificate agent and 7.91% for cell coithout interface modification agent). |
