Compact Titania Films by Spray Pyrolysis for Application as ETL in Perovskite Solar Cells
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https://doi.org/10.1007/s11664-020-08464-5 Ó 2020 The Minerals, Metals & Materials Society
Compact Titania Films by Spray Pyrolysis for Application as ETL in Perovskite Solar Cells SOORAJ KUMAR,1 ASIM AFTAB,1 and MD. IMTEYAZ AHMAD1,2 1.—Department of Ceramic Engineering, Indian Institute Varanasi 221005, India. 2.—e-mail: [email protected]
of
Technology
(BHU),
Hybrid perovskite-based solar cells are projected as a potentially viable photovoltaic (PV) technology for large-scale implementation. The electron transport layer (ETL) should be dense and pinhole-free to facilitate efficient electron collection and transport from the perovskite layer to the anode, which is very important for achieving high-performance solar cells. In this study, a compact TiO2 layer was synthesized by a scalable spray pyrolysis technique. The effect of deposition temperature on the transparency, microstructure, and bandgap of c-TiO2 film was studied. Pinhole-free nanocrystalline films having > 85% transparency with uniform coverage was obtained on spray pyrolysis at 400°C and annealing at 450°C. Usability of the deposited films as ETL in perovskite solar cells was tested by fabricating solar cells (FTO/c-TiO2/ FA0.85MA0.15Pb(I0.85Br0.15)3/CuSCN/Au) using the deposited films and comparing their performance. Cell efficiency close to 11.75% with a fill factor of 69% was obtained in the cell fabricated using the films deposited at 400°C. Key words: Titania thin film, electron transport layer, perovskite solar cells, spray pyrolysis
INTRODUCTION Hybrid perovskite solar cells (PSC) have demonstrated unprecedented progress in efficiency, and its architecture has evolved over the last 8–9 years, achieving the highest power conversion efficiency of about 25.2%.1 Owing to its unprecedented progress, perovskite solar cells (PSCs) are promising candidates for large-scale implementation with the potential to replace the existing commercial photovoltaic (PV) technologies.2 PSCs posses several outstanding properties such as unique electronic structure, bandgap tunability, superior charge transport properties, facile processing, and low cost, making them promising as photovoltaic devices.3 However, substantial challenges remain, which include stability under ambient conditions, scalability to industrial production, and hysteresis in the J-V curve. In a typical PSC, sunlight is absorbed
(Received March 21, 2020; accepted September 1, 2020)
mainly by the perovskite layer resulting in the generation of charge carriers (electrons and holes). The holes travel through the hole transport layer (HTL) to be collected at the counter electrode (generally Au or Ag), while the electrons are transported to the anode through the electron transport layer (ETL). Scalable deposition of the charge-transport layers (ETL and HTL) is crucial for implementing PSCs at larger scales.4 In order to fabricate PSCs with high efficiency, the materials selected for the ETL must fulfil several criteria. The ETLs must possess good electron mobility to enable fast electr
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