Chu, C.-Y.C.-Y.ChuChang, C.-Y.C.-Y.ChangSu, W.-F.W.-F.SuWEI-FANG SU2018-09-102018-09-102016http://www.scopus.com/inward/record.url?eid=2-s2.0-84963692242&partnerID=MN8TOARShttp://scholars.lib.ntu.edu.tw/handle/123456789/399407Recently, the perovskite solar cells draw lots of attentions because of low cost, solution-processable and promising high efficiency. The power conversion efficiency (PCE) is rapidly reached to a certified value of 20.1%. However, the conventional electron transport layer (ETL) of the device needs to be sintered over 500 °C which is high energy-consumption process and cannot use on flexible substrate. Therefore, many research groups endeavor to develop low-temperature solution processable electron transport material in perovskite solar cells. In this review, we present systematic and critical discussions on the evolution of perovskite solar cells from meso-superstructure solar cells (MSSCs) to low-temperature solution processed planar heterojunction (PHJ) perovskite solar cells. This review will provide a guideline for the fabrication of high PCE perovskite solar cell using solution process at temperature of 150 °C or under, which has potential to achieve large scale fabrication by roll-to-roll technique for commercial products in near future. © 2016 The Japan Society of Applied Physics.[SDGs]SDG7Electron transport properties; Energy utilization; Heterojunctions; Perovskite; Perovskite solar cells; Sintering; Temperature; Critical discussions; Electron transport layers; Electron transport materials; High energy consumption; Large-scale fabrication; Low temperature solutions; Power conversion efficiencies; Roll-to-roll techniques; Solar cellsjournal article10.7567/JJAP.55.04EA01