以溶膠凝膠法於低溫下製備氧化錫薄膜作為鈣鈦礦太陽能電池之電子傳輸層

Abstract

氧化錫是常用於有機無機混合鈣鈦礦太陽能電池電子傳輸層的材料之一，因為它具有高的載子遷移率，能階也與鈣鈦礦相匹配。目前文獻中對於做為電子傳輸層的低溫製程氧化錫薄膜，通常是使用旋塗氧化錫奈米顆粒懸浮液的方式製備。雖然使用此方法製備電子傳輸層的鈣鈦礦太陽能電池已能達到高效率，在前驅物準備上仍較複雜。為了找到一種更簡單的方法，此篇研究利用高反應性有機錫前驅物—異丙醇錫，透過較簡單的溶膠凝膠法在低溫下製備高品質的氧化錫薄膜，其電導率大於3.1 × 10-3 S/cm，也成功以此氧化錫薄膜做為鈣鈦礦太陽能電池之電子傳輸層，此太陽能電池元件的能量轉換效率可達15%。接著我們進一步研究此氧化錫薄膜的成膜機制，藉由化學和表面分析，發現燒結環境的相對濕度是影響氧化錫成膜的重要因素。相對濕度高的燒結環境可使反應中濕膜的乾燥時間拉長，令中間產物有足夠的時間進行縮合反應，使得反應更完全，最終得到具較低電阻的高品質氧化錫電子傳輸層。

Tin oxide (SnOx) is one of the commonly used electron transporting materials for organic-inorganic hybrid perovskite solar cells (PSCs) as well as other types of electronic devices thanks to its excellent electronic properties. Currently, low-temperature, solution-based processing of SnOx films for electron transporting applications have relied upon casting from dispersion solutions of pre-synthesized SnOx nanocrystals. Aiming for a simpler method, this study demonstrated a low-temperature sol-gel process for fabricating high-quality SnOx films utilizing a high-reactivity organotin precursor, tin (IV) isopropoxide (TIP). The key to obtaining high electrical conductivity from the sol-gel SnOx films at low processing temperatures was identified to be a high-humidity annealing environment. By using > 70% relative humidity (R.H.), SnOx films with conductivity > 3.1 × 10-3 S/cm could be fabricated at annealing temperatures ranging from 25 to 85 C, which when incorporated into PSC devices as electron-transporting layers yielded power conversion efficiency > 15%. Chemical and surface analysis revealed that the beneficial effects of the high-humidity annealing environment originated from the slower sol-gel condensation reaction rates at higher R.H., which allowed more thorough removal of reaction byproducts, resulting in lower impurity in the SnOx films.