Mesoscopic perovskite solar cells with an admixture of nanocrystalline TiO and AlO: role of interconnectivity of TiO in charge collection

• Published in: Nanoscale 2016-03, Vol.8 (12), p.6341-6351
• Main Authors: Cha, Jae-Min, Lee, Jin-Wook, Son, Dae-Yong, Kim, Hui-Seon, Jang, In-Hyuk, Park, Nam-Gyu
• Format: Article
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c5nr05974g

Perovskite solar cells with high power conversion efficiency usually employ mesoporous TiO 2 , however the role of the TiO 2 layer has not been clearly resolved. Here we prepared MAPbI 3 (MA = CH 3 NH 3 ) perovskite solar cells with an admixture of nanocrystalline TiO 2 and Al 2 O 3 to investigate the role of the mesoporous TiO 2 layer. The Al 2 O 3 content was varied from 0% (pure TiO 2 ) to 100% (pure Al 2 O 3 ) with nominal composition of (1 − x )TiO 2 + x Al 2 O 3 ( x = 0, 0.25, 0.5, 0.75 and 1). The photocurrent density and fill factor decreased as Al 2 O 3 content increased, whereas the open-circuit voltage was hardly changed. Steady-state photoluminescence (PL) was less quenched as the Al 2 O 3 content increased due to its non-electron-injecting characteristics, where a decrease in PL intensity with increasing TiO 2 content was correlated to an increase in photocurrent. Electron injection to TiO 2 was also evidenced by time-resolved PL and time-limited photocurrent measurements, where interconnection of TiO 2 particles played an important role in charge collection. The slight change in voltage with Al 2 O 3 content was explained by balancing the Fermi position due to a trade-off between charge recombination and the Fermi level. The results observed from the admixture mesoporous layer comprising electron-injecting and electron-non-injecting oxides suggest that electron-injection characteristics play an important role in determining photovoltaic parameters. Perovskite solar cells with an admixture of nanocrystalline TiO 2 and Al 2 O 3 are prepared to explore the role of the mesoporous TiO 2 layer: interconnection of TiO 2 particles plays an important role in charge collection.