Suppression of Photovoltaic Losses in Efficient Tandem Organic Solar Cells (15.2%) with Efficient Transporting Layers and Light Management Approach

Organic solar cells (OSCs) have experienced a rapid progress in terms of efficiency in both single and tandem structures. Herein, two-terminal (2T) tandem design is fabricated using PV2000:PCBM (1.65 eV) and PM6:Y6 (1.3 eV) blends as bottom and top cells, respectively. The role of transporting and recombination layers on photovoltaic (PV) parameters is studied. The impedance and transmittance results indicate that using SnO2 nanocrystals (NCs) as an electron transporting layer (ETL) in both subcells, the fill factor (FF) and the open circuit voltage (V-OC) of the tandem device are increased drastically, mainly due to the lower resistance of the SnO2 layer and its higher transmittance as compared with the ZnO ETL. Moreover, it is found that the V-OC and FF losses are reduced using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/Ag (1 nm)/SnO2 NCs as a recombination layer in the tandem design. After proper optimization, a tandem OSC with a V-OC of 1.61 V and an efficiency of 14.4% is achieved, which shows great operational stability as well. In addition, the current match and efficiency of the tandem device are increased up to 12.94 mA cm(-2) and 15.2%, respectively, by applying a nanotextured anti-reflection layer on the back of the device.

Automated summary

The study investigates the impact of transporting and recombination layers on the photovoltaic parameters of two-terminal tandem organic solar cells, finding that using SnO2 nanocrystals as an electron transporting layer and a specific recombination layer can significantly increase the fill factor and open circuit voltage.