Gelation of Hole Transport Layer to Improve the Stability of Perovskite Solar Cells

To achieve high power conversion efficiency(PCE) and long-term stability of perovskite solar cells(PSCs), a hole transport layer(HTL) with persistently high conductivity, good moisture/oxygen barrier ability, and adequate passivation capability is important. To achieve enough conductivity and effective hole extraction, spiro-OMe TAD, one of the most frequently used HTL in optoelectronic devices, often needs chemical doping with a lithium compound(LiTFSI). However, the lithium salt dopant induces crystallization and has a negative impact on the performance and lifetime of the device due to its hygroscopic nature. Here, we provide an easy method for creating a gel by mixing a natural small molecule additive(thioctic acid, TA) with spiro-OMe TAD. We discover that gelation effectively improves the compactness of resultant HTL and prevents moisture and oxygen infiltration. Moreover, the gelation of HTL improves not only the conductivity of spiro-OMe TAD, but also the operational robustness of the devices in the atmospheric environment. In addition, TA passivates the perovskite defects and facilitates the charge transfer from the perovskite layer to HTL. As a consequence, the optimized PSCs based on the gelated HTL exhibit an improved PCE(22.52%) with excellent device stability.

Perovskite quantum dot microarrays:In situ fabrication via direct print photopolymerization

Quantum dots color conversion(QDCC)is considered as a facial and versatile way to achieve full-color organic light emitting diode(OLED)and micro-LED display due to the wide color gamut performance and easy integration.However,the aggregation of QDs and coffee-ring effects after solvent evaporation lowers the light conversion efficiency and emission uniformity in QDs microarrays,raising blue-light leakage or optical crosstalk.Here,we report the fabrication of perovskite quantum dots(PQDs)microarrays by combining the inkjet printing and in situ fabrication of PQDs during the photopolymerization of precursor ink.The resulting PQDs microarrays exhibit three-dimensional(3D)morphology with hemisphere shape as well as strong photoluminescence,which is desirable for QDCC applications.We demonstrate the dominant role of ultraviolet(UV)curable precursors and surface functionalized substrate in controlling the shape of microarrays,where significantly increased contact angle(100°)and large height to diameter ratio(0.42)can be achieved.We further demonstrate the potential use of the in situ direct print photopolymerization method for fabricating large-area multicolor patterned pixel microarrays with a wide color gamut and high resolution.The fabrication of 3D PQDs microarrays opens up new opportunities in a variety of applications including photonics integration,micro-LED,and near-field display.