Azahomofullerenes as New n-Type Acceptor Materials for Efficient and Stable Inverted Planar Perovskite Solar Cells

Optimizing PEDOT:PSS with a Sodium Lignosulfonate Additive to Improve the Performance of Inverted Perovskite Solar Cells

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is considered to be a highly desirable hole transport material for inverted perovskite solar cells (PSCs) because of its low cost, simple preparation process, and high light transmittance. Unfortunately, its inherent drawbacks, such as suboptimal electrical conductivity and high interfacial defect density, hamper charge extraction efficiency and ultimately limit device performance. In this work, we incorporated an environmentally friendly additive, sodium lignosulfonate (LS), into PEDOT:PSS to enhance the photovoltaic performance of inverted PSCs. The optimized device with a 0.1 mg/mL LS-doped hole transport layer (HTL) displayed a significant increase in power conversion efficiency from 15.36% of the reference device (with pristine PEDOT:PSS HTL) to 17.28%. LS doping did not influence the morphology of the PEDOT:PSS film and the overlying perovskite film. Instead, it serves a dual function: improving conductivity to enhance hole extraction ability and reducing interface defects to decrease nonradiative recombination losses. Therefore, this work presents a straightforward and efficient additive engineering strategy to enhance the electrical performance of inverted PSCs.

Potassium stearate doped PEDOT:PSS improves the performance of inverted perovskite solar cells

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) suffers from lower conductivity and surface defects, which hinders the extraction and transport of effective charges, thereby reducing the Power conversion efficiency (PCE) and long-term stability of PSCs. Therefore, this study introduces potassium stearate (KSt) doping in PEDOT:PSS to regulate its conductivity and interface charge transfer. As a result, KSt-doped PEDOT:PSS increase the PCE of the device from 16.35% to 18.35%. Moreover, the PCE of PSCs with KSt-doped PEDOT:PSS can maintain 87% of its initial value after being stored in a glove box for over 700 hours. This work provides a simple and effective method for designing high-performance and stable PSCs.

Enhancing charge extraction in inverted perovskite solar cells contacts via ultrathin graphene:fullerene composite interlayers

Improving the perovskite/electron-transporting layer (ETL) interface is a crucial task to boost the performance of perovskite solar cells (PSCs). This is utterly fundamental in an inverted (p-i-n) configuration using fullerene-based ETLs. Here, we propose a scalable strategy to improve fullerene-based ETLs by incorporating high-quality few-layer graphene flakes (GFs), industrially produced through wet-jet milling exfoliation of graphite, into phenyl-C61-butyric acid methyl ester (PCBM). Our new composite ETL (GF:PCBM) can be processed into an ultrathin (∼10 nm), pinhole-free film atop the perovskite. We find that the presence of GFs in the PCBM matrix reduces defect-mediated recombination, while creating preferential paths for the extraction of electrons towards the current collector. The use of our GF-based composite ETL resulted in a significant enhancement in the open circuit voltage and fill factor of triple cation-based inverted PSCs, boosting the power conversion efficiency from ∼19% up to 20.8% upon the incorporation of GFs into the ETL.

Thieno[3,2-b]indole–benzo[b]thieno[2,3-d]thiophen-3(2H)-one-based D–π–A molecules as electron transport materials for perovskite solar cells

New small molecule D–π–A compounds, bearing thieno[3,2-b]indole and benzo[b]thieno[2,3-d]thiophen-3(2H)-one scaffolds, were prepared, characterized and utilized as electron transport materials in perovskite solar cells.