Enhanced photo-stability of inverted organic solar cells via using polyethylenimine in the electron extraction layers

Significant enhancement in quantum-dot light emitting device stability via a ZnO:polyethylenimine mixture in the electron transport layer

“…Instead, mixing the PEI into the ZnO in the form of a ZnO:PEI blended ETL instead of a separate layer has therefore been recently proposed 29 , similar to what was done in OLEDs [29][30][31] and OSCs. [32][33][34][35][36] In the only report applying a ZnO:PEI(E) ETL to QDLEDs, Shi et al showed that using a ZnO:PEIE blended ETL can improve the efficiency of inverted blue QDLEDs but its effect on stability was not addressed. 37 In this work, we investigate and compare between using ZnO:PEI blended ETL and a bilayer ZnO/PEI ETL structure on device performance in inverted red QDLEDs.…”

The Use of Green‐Solvent Processable Molecules with Large Dipole Moments in the Electron Extraction Layer of Inverted Organic Solar Cells as a Universal Route for Enhancing Stability

“…[12] Therefore, in most cases, an electron extraction layer (EEL) is used in between the ITO electrode and active layer. [13][14][15][16][17][18] The EEL, usually made of a solution-processable wide bandgap metal oxide, blocks the extraction of photogenerated holes from the active layer by the ITO and thus enhances the electron selectivity for the ITO/EEL contact. ZnO has been the most commonly used material for that purpose owing to its low toxicity, high electron mobility, inherent transparency, and a large energetic barrier against holes (often more than 1 eV).…”

“…ZnO has been the most commonly used material for that purpose owing to its low toxicity, high electron mobility, inherent transparency, and a large energetic barrier against holes (often more than 1 eV). [19,20] This energy barrier can prevent hole collection/injection at typical operation temperatures and thus enhances the hole-blocking functionality.…”

“…[21][22][23][24][25] Some approaches have been proposed to overcome this UV-induced degradation, such as applying UV treatments to the ZnO layer before active layer deposition, [26] adding a bilayer EEL, [25] or doping the ZnO layer. [20,27] These methods, however, increase the manufacturing complexity and cost. Replacing ZnO with SnO x [21] or selfassembled monolayers (e.g., C 60 -SAMs) [11] can lead to significant photostability benefits, but the higher toxicity or the need for halogenated solvents reduce the viability of these alternatives.…”

Significant Photostability Enhancement of Inverted Organic Solar Cells by Inserting an N-Annulated Perylene Diimide (PDIN-H) between the ZnO Electron Extraction Layer and the Organic Active Layer

“…With power conversion efficiencies (PCEs) exceeding 17% being reported recently, organic solar cells (OSCs) are now approaching the level of efficiency that is required for commercial applications. − However, their limited stability remains one of the major obstacles preventing their adoption . The degradation in OSCs is mostly caused by air or sunlight, referred to as ambient-induced and photoinduced degradation, respectively. , Ambient-induced degradation can be effectively controlled via proper encapsulation. , It can also be improved by replacing the “conventional” solar cell geometry with an “inverted” one in which the low work function (WF) cathode is used as a bottom electrode rather than a top one, thereby minimizing ambient exposure of the low WF metal. ,, Photoinduced degradation is, however, more challenging to manage and thus remains a leading failure mode in OSCs. − It has been shown that the choice of the electron extraction layer (EEL), which is used in between the ITO electrode and the organic active layer in inverted OSCs, plays a critical role in device photostability. − The EEL function is two-fold: (i) facilitating electron collection by the contact and (ii) preventing the leakage or neutralization of holes (via recombination with electrons) at the contact interface. ZnO, as an n-type wide bandgap metal oxide, has been the most commonly used EEL owing to its easy processing, , good transparency in the visible range of the solar spectrum, relatively high electron mobility, and high ambient stability. ,− OSCs with a ZnO EEL, however, have several limitations.…”