Organic solar cells (OSCs) are promising renewable energy sources for replacing fossil fuels. The power conversion efficiency (PCE) of OSCs has increased based on tremendous effort in material and device engineering. Still, the stability of OSC, such as long lifetime, negative temperature coefficient, must be enhanced for commercialization. In this study, we investigated OSC performance at a high operating temperature near 300–420 K, which are typical temperature regions in photovoltaic applications, with a different hole-extraction layer (HEL). The metal oxide-based HEL, MoO3, exhibited stable operating properties with a PCE drop rate of −0.13%/°C, as compared to polymeric HEL, PEDOT:PSS (−0.20%/°C). This performance reduction of polymeric HEL originated from the degradation of the interface in contact with PEDOT:PSS, as compared to the robust inorganic metal oxide HEL.

QD-LEDs have gained tremendous attention to potentially replace current emissive display technologies. Here, we explore solution-processable SnO2 nanoparticles (NPs) as alternatives to ZnO for the electron transporting layer in QD-LEDs.

Colloidal quantum dots (QDs) have many advantages in optoelectronic applications such as light‐emitting diodes (LEDs), solar cells, and photocatalysts because of their superb optical and electrical properties that can be tuned by changing the shapes and sizes of the QDs. The efficiency of QD‐LEDs is significantly improved as inorganic metal oxide nanoparticles (NPs) are adopted for electron transport layers (ETLs) because of the high electron mobility of the NPs. However, there are two significant drawbacks of the ETLs with metal oxide NPs that hinder device performance and stability: low compactness of the metal oxide NP films that generate a massive leakage current pathway and charge imbalance caused by spontaneous electron injection from metal oxide ETLs into the QDs. To address these drawbacks, an organic/inorganic double ETL is introduced consisting of 1,3,5‐tris(2‐N‐phenylbenzimidazolyl)benzene (TPBi) and zinc oxide (ZnO) NPs. By depositing TPBi on the ZnO NP ETL, the pinholes and cracks present in the ZnO NP layer are filled successfully, preventing the leakage current pathway. Furthermore, TPBi also works as a “charge balancer” by suppressing spontaneous electron injection from the ETL into the QDs. As a result, twice the external quantum efficiency and three times the lifetime are obtained with the blue QD‐LEDs.