Efficient Organic Photovoltaics with Improved Charge Extraction and High Short-Circuit Current

Abstract

Exciton generation, dissociation, free carrier transport, and charge extraction play an important role in the short-circuit current (J sc) and power conversion efficiency of an organic bulk heterojunction (BHJ) solar cell (SC). Here we study the impact of band offset at the interfacial layer and the morphology of active layer on the extraction of free carriers. The effects are evaluated on an inverted BHJ SC using zinc oxide (ZnO) as a buffer layer, prepared via two different methods: ZnO nanoparticle dispersed in mixed solvents (ZnO A) and sol–gel method (ZnO B). The device with ZnO A buffer layer improves the charge extraction and J sc. The improvement is due to the better band offset and morphology of the blend near the ZnO A/active layer interface. Further, the numerical analysis of current–voltage characteristics illustrates that the morphology at the ZnO A/active layer interface has a more dominant role in improving the performance of the organic photovoltaic than the band offset.

Polymer‐Modified ZnO Nanoparticles as Electron Transport Layer for Polymer‐Based Solar Cells

“…This indicates that the ETL surface roughness may also affect the morphology of the active layer. [28] The change in the film quality can also be seen by SEM (Figure 2a-c). In Figure 2a, the pure ZnO NP ETL shows a poorly packed, non-uniform assembly of the ZnO NPs.…”

“…Dispersions of ZnO nanoparticles (NPs) can be used to produce ETLs with thicknesses >100 nm [27] without the use of high temperature thermal annealing. [28] However, in comparison to the solgel ZnO, the size of the ZnO NPs is much larger which may lead to larger interstitial regions between the NPs and pinholes in the film that deleteriously effects electron mobility and makes the active layer more susceptible to the effects of water and oxygen. [29] In addition, any aggregation of the NPs in the dispersion and the deposition of the hydrophilic NPs on a hydrophobic surface, that could result in dewetting, would lead to non-uniformities in the films, and reduced carrier extraction efficiency from active layer to ETL.…”

Futuristic electron transport layer based on multifunctional interactions of ZnO/TCNE for stable inverted organic solar cells

“…23,24 Additionally, they create adsorption sites for environmental oxygen and water molecules, which are highly detrimental to device stability. 25,26 Consequently, the surface defect passivation strategy of ZnO has become vital concurrently in enhancing the PCE and the sustainability of inverted OSCs.…”

Physicochemical Studies on Nafion® Modified ZnO Interlayers for Enhanced Electron Transport in the Inverted Polymer Solar Cells

“…It should be noted that replacing PEDOT:PSS with metal oxide based HTLs typically lead to a reduction of R s resulting in better efficiency . Mohan et al . reported the fabrication of 5.6% efficiency cell with P3HT:PC 71 BM by using this strategy.…”