Super Flexible Transparent Conducting Oxide‐Free Organic–Inorganic Hybrid Perovskite Solar Cells with 19.01% Efficiency (Active Area = 1 cm2)

Abstract

Highly efficient organic–inorganic hybrid perovskite solar cells (OIHP‐SCs) are often fabricated on a transparent conducting oxide (TCO) substrate such as indium tin oxide (ITO). However, the presence of TCOs is disadvantageous to the development of flexible OIHP‐SCs due to the brittle nature of ITO which is easily breakable during bending. Herein, a flexible TCO‐free OIHP‐SC is demonstrated by using lithium bis(trifluoromethane)sulfonimide (Li‐TFSI) as a codopant for the single‐layer graphene transparent conducting electrode and poly(triarylamine) hole‐transporting material (HTM) on a flexible polydimethylsiloxane substrate. The optical and electrical properties of the Li‐TFSI‐doped graphene substrate are measured by controlling the doping amount and the best conditions for charge extraction are established at a doping concentration of 20 mm Li‐TFSI, thus optimizing the device photovoltaic performance. As a result, a highest power conversion efficiency of 19.01% is demonstrated by the flexible TCO‐free OIHP‐SC devices with an active area of 1 cm2. In addition, the flexible TCO‐free OIHP‐SCs exhibit good bending stability after 5000 bending cycles at radii of 6, 4, and 2 mm and excellent light soaking stability under 1 Sun light intensity over 1000 h as opposed to the poor stability when using poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate as the HTM.