A facile approach for enhancing device performance of excitonic solar cells with an innovative SnO2/TCNE electron transport layer

Abstract

The spread of the Internet of things created the need for huge amounts of off-grid energy sources for tens of billions of electronic devices with low power consumption for indoor applications. Excitonic solar cells may provide a better solution as compared with other solar cells due to their advantages such as low-cost, large-area module, and fabrication by solution printing and coating techniques. However, the organic solar cells (OSCs) or perovskite solar cells (PSCs) should have a low energy loss, suitable absorption spectrum, and minimum trap mediated charge recombination for its proper commercialization. Interface engineering is one of the ways of achieving better performance for these devices. Herein, we report a facile and effective strategy for interfacial modulation to achieve the improved performance of inverted bulk heterojunction (BHJ) solar cells with a solution-processable SnO2 electron transport layer (ETL) modified by an organic small molecule tetracyanoethylene (TCNE). We can say that a few nano-meter thin film of TCNE supports to reduce the energy barrier of SnO2, resulting in the efficient extraction and transport of negative charge carriers toward the cathode. The TCNE also passivates the surface defects of SnO2 and hence decreases the charge recombination rate for iOSCs. Furthermore, it brings the better interfacial contact between SnO2 and BHJ blend in which the polymer PTB7 and fullerene PC71BM are the donor and acceptor, respectively, showing average power conversion efficiencies of ∼4.58%, ∼4.98%, and ∼2.95% with varying concentrations of TCNE (0.5 mg/ml, 1 mg/ml, and 2 mg/ml), respectively, in methanol, on top of SnO2, as ETLs, which are comparably better than that of pristine SnO2 (3.28%). We assumed that the TCNE modified SnO2 method is a potent and easy way to get efficient inverted BHJ solar cells with higher efficiency and may also be an appropriate alternative for other organic semiconducting devices where an ETL is required, such as organic light-emitting diodes and PSCs.