The staggered type heterojunction with g-C3N4 based nanomaterials has inspired much attention owing to its change in chemical potential between the two semiconductors. As a result, the migration of charge...
The design and development of a charge carrier transport material are decisive parameters for controlling the organic solar cell's power conversion efficiency (PCE). ZnO is one of the most suitable electron transport materials used in inverted bulk heterojunction polymer solar cells. However, the solution‐processed ZnO has surface defects, which hinders the power conversation efficiency of the device. Herein, it is designed and demonstrated that the 2D NO2 group functionalized reduced graphene oxide (rGN) sheet coated on top of the 1D ZnO nanoridges not only passivates the surface but also enhances the charge transport property of the electron transport layer (ETL), thereby improving the overall PCE by 31%. Atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and optical measurements reveal that the highly transparent bilayer ZnO/rGN ETL has uniform film formation and, thereby, improved ohmic contact between the cathode and the photoactive layer. Due to the improved electron transport from the photoanode (PTB7‐Th:PC71BM) to the buffer layer, a photoinduced current density of 20.05 mA cm−2 is achieved. This interface modification by rGN can be an effective strategy to passivate the surface and retards the recombination rate to enhance the efficiency of organic photovoltaic cells.
The light soaking process is a well-known technique to mitigate defects on the surface and the energy band mismatch of the TiO 2 -based cathode interfacial layer (CIL) in organic solar cells (OSCs). However, the excess energy consumption by the light soaking process strongly hampers the commercially viable fabrication of OSC devices. In this study, without adopting the light soaking treatment, we improved the power conversion efficiency (PCE) of organic solar cells based on the TiO 2 CIL by heteroatom (N and S) passivation and graphene incorporation. The N, S doping passivates the positively charged trap states (oxygen vacancy), and graphene incorporation enhances the carrier transportation of the TiO 2 CIL. Interestingly, without light soaking treatment, ∼100 times enhanced electron mobility and ∼5 times shorter charge carrier lifetime are achieved with the heteroatom passivated (N and S) and graphene incorporated TiO 2 CIL (TUG-TiO 2 ), in contrast to the bare TiO 2 CILbased devices. The improvement in the carrier mobility of the TUG-TiO 2 CIL is examined by ultraviolet photoelectron spectroscopy and Kelvin probe measurement. Moreover, the OSC device fabricated with TUG-TiO 2 CIL along with PTB7-Th:PC 71 BM (ITO/TUG-TiO 2 /PTB7-Th:PC 71 BM/MoO 3 /Ag) as an active layer exhibits PCE up to 10.72% than its counter device (ITO/TiO 2 /PTB7-Th:PC 71 BM/ MoO 3 /Ag and PCE is 6.18%), without compromising the stability. This work spotlights the salient feature of defect passivation on TiO 2 for the enhancement in PCE and the stability of organic solar cells and also highlights an alternative strategy to avoid the light soaking treatment.
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