No abstract

Hybrid solar cells (HSCs) incorporating both organic and inorganic materials typically have significant interfacial issues which can significantly limit the device efficiency by allowing charge recombination, macroscopic phase separation, and nonideal contact. All these issues can be mitigated by applying carefully designed interfacial modifiers (IMs). In an attempt to further understand the function of these IMs, we investigated two IMs in two different HSCs structures: an inverted bilayer HSC of ZnO:poly(3-hexylthiophene) (P3HT) and an inverted bulk heterojunction (BHJ) solar cell of ZnO/P3HT:[6,6]-phenyl C61-butyric acid methyl ester (PCBM). In the former device configuration, ZnO serves as the n-type semiconductor, while in the latter device configuration, it functions as an electron transport layer (ETL)/hole blocking layer (HBL). In the ZnO:P3HT bilayer device, after the interfacial modification, a power conversion efficiency (PCE) of 0.42% with improved Voc and FF and a significantly increased Jsc was obtained. In the ZnO/P3HT:PCBM based BHJ device, including IMs also improved the PCE to 4.69% with an increase in Voc and FF. Our work clearly demonstrates that IMs help to reduce both the charge recombination and leakage current by minimizing the number of defect sites and traps and to increase the compatibility of hydrophilic ZnO with the organic layers. Furthermore, the major role of IMs depends on the function of ZnO in different device configurations, either as n-type semiconductor in bilayer devices or as ETL/HBL in BHJ devices. We conclude by offering insights for designing ideal IMs in future efforts, in order to achieve high-efficiency in both ZnO:polymer bilayer structure and ZnO/polymer:PCBM BHJ devices.

The difluorobenzene-incorporated polymer showed strong ordering in edge-on mode, resulting in a significant reduction in the leakage current, and thus PFBT2OBT:PC70BM devices showed highly improved detectivity of over 1013 Jones at −2V.

Porphyrin derivatives have recently emerged as hole transport layers (HTLs) because of their electron-rich characteristics. Although several successes with porphyrin-based HTLs have been recently reported, achieving excellent solar cell performance, the chances to improve this further by molecular engineering are still open. In this work, Zn porphyrin (PZn)-based HTLs were developed by conjugating fluorinated triphenylamine (FTPA) wings at the perimeter of the PZn core for low-temperature perovskite solar cells (L-PSCs). The fluorinated PZn-HTLs (PZn–2FTPA and PZn–3FTPA) exhibited superior HTL properties compared to the nonfluorinated one (PZn–TPA). Moreover, their deeper highest occupied molecular orbital energy levels were beneficial for boosting open-circuit voltages, and their enhanced face-on stacking improved the hole transport properties. The L-PSC using PZn–2FTPA achieved the highest performance of 18.85%. Thus far, this result is one of the highest reported power conversion efficiencies among the PSCs using porphyrin-based HTLs.