| 摘要: | 鈣鈦礦太陽能電池(Perovskite solar cells，簡稱PSC)由於組裝過程簡易且使用的原料少，因此製作成本低而快速發展。至2020年PSC元件已驗證的光電轉換效率已達25.2%。PSC元件中所使用的電子傳遞層(electron transporting layer, ETL)材料須具備高電子萃取效率、快速電子傳遞及和鈣鈦礦層的valence band(VB)與conduction band(CB)能階匹配等特性。以低溫方式製備的TiO2膜雖然有利於低成本製造，但低溫製備的TiO2膜有低電子萃取能力及低導電度之缺點，導致所組裝的一般式PSC元件有嚴重的遲滯現象。本研究透過在TiO2奈米粒子懸浮液中添加高導電度SnO2奈米粒子在低溫下製備SnO2:TiO2膜(SnO2與TiO2奈米粒子混合所製備的膜)，並且在SnO2:TiO2膜上再沉積一層SnO2膜形成雙層膜(SnO2:TiO2/SnO2)，以此雙層膜作為電子傳遞層所組裝的鈣鈦礦太陽能電池比以TiO2/SnO2雙層膜及SnO2 or SnO2:TiO2 or TiO2單層膜為ETL的元件有較高的光電轉換效率。SnO2的添加能增加低溫製備之TiO2膜的導電度，SnO2:TiO2/SnO2膜的導電度(1.48×10-3 mS/cm)比TiO2膜(1.03×10-3 mS/cm)高，TiO2膜的CB能階為-4.40 eV，而雙層ETL中的SnO2:TiO2與SnO2的CB能階分別為-4.29 eV及-4.07 eV與鈣鈦礦膜的CB能階-4.02 eV匹配性比TiO2 ETL更好，因此有更好的電子萃取/導通能力，雙層ETL可以快速地將鈣鈦礦膜VB上受光激發至CB的電子萃取出來並傳遞至FTO導電玻璃上。而SnO2與FTO相容性不夠好，因此沉積在FTO上的SnO2膜不是很均勻連續，但在含有SnO2:TiO2膜上所再沉積一層SnO2膜的表面形貌連續平整且有高親水性，使得鈣鈦礦膜沉積在雙層膜上有較大的顆粒以SnO2:TiO2/SnO2為ETL所組裝之元件的光電轉換效率可達22.16%且元件的遲滯因子僅1%比用單層TiO2作為ETL之元件的光電轉換效率(18.48%)高、遲滯因子(52%)小。以SnO2:TiO2/SnO2及TiO2/SnO2雙層ETL所組裝之元件放置在手套箱1512小時的光電轉換效率為原效率的94%及93%，以SnO2、SnO2:TiO2及TiO2單層為ETL之元件的光電轉換效分別為原效率的94%、84%及85%。若元件未封裝放置在大氣下(25~30°C，相對溼度40-50%)48小時後，以SnO2:TiO2/SnO2及TiO2/SnO2雙層ETL所組裝之元件的光電轉換效率為原效率的33%及31%；以SnO2為ETL的元件效率只剩18%、而以SnO2:TiO2及TiO2為ETL之元件已量不到光電轉換效率。;The rapid progree of perovskite solar cell (PSC) is due to it has a simple assembly process, high efficiency and uses few materials, therefore the manufacturing cost is low. The certified power conversion efficiency (PCE) of PSC device has reached 25.2% in 2020. Electron transporting layer (ETL) used in PSC devices must have high electron extraction efficiency, fast electron transfer and the energy band matching those (valence band (VB) and conduction band (CB)) of the perovskite absorber. TiO2 ETL prepared at low temperature is beneficial to cost of manufacture, nevertheless, TiO2 film prepared at low temperature has the shortcomings of low electron extraction ability and low conductivity, which result in serious hysteresis and poor long-term stability when used in the regular typed PSC. In this study, high conducting SnO2 nanoparticles was added into TiO2/EtOH suspension to prepare SnO2:TiO2 nanocomposite film at low temperature by spin-coating. Furthermore a layer of SnO2 film was deposited on top of SnO2:TiO2 nanocomposite film to form a double-layer (SnO2:TiO2/SnO2) ETL, perovskite solar cell based on the double-layer ETL has higher PCE than those used SnO2 or SnO2:TiO2 or TiO2 single-layer film as an ETL. The addition of SnO2 can increase the electrical conductivity of the TiO2 film prepared at low temperature. The CB energy level of the TiO2 film is -4.40 eV, while the CB energy levels of SnO2:TiO2 and SnO2 in the double-layer ETL are -4.29 eV and -4.07 eV, respectively. The CB energy level of the perovskite film (-4.02 eV) has a better match to SnO2:TiO2/SnO2 than to TiO2 film. Therefore double-layer SnO2:TiO2/SnO2 ETL has better electron extraction ability compared to single-layer ETL. Furthermore, the surface morphology of the SnO2 filmdeposited on the SnO2:TiO2 is dense and flat.The high hydrophilicity surface of double-layer SnO2:TiO2/SnO2 ETL makes the desposited perovskite film has large particles. The PCE of the devicebased on SnO2:TiO2/SnO2 ETL reaches 22.16%, with very low hysteresis index of only 1%. On the other hand, PSC used TiO2 film as an ETL has a low PCE (18.48%) and high hysteresis index (52%). PSC based on SnO2:TiO2/SnO2 and TiO2/SnO2 ETL maintain 94% and 93% of the original PCE when places in the glove box for 1512 hours. While the devices used SnO2, SnO2:TiO2, and TiO2 as ETLs retain the PCE of 94%, 84%,and 85%, respectively. When the devices were placed in air without encapsulation for 48 hours, cells based on double-layer SnO2:TiO2/SnO2 and TiO2/SnO2 ETLs still have 34% and 33% of their original efficiency. Nevertheless, the PCE of the devices used single layer SnO2, SnO2:TiO2, and TiO2 ETL is close to zero. |
