Effect of UV-ozone process on the ZnO interlayer in the inverted organic solar cells

Abstract

ZnO interlayer is crucial for the performance of inverted organic solar cells (IOSCs). Herein, we investigate the effects of short UV-ozone treatment of ZnO nanofilms (ZnONFs) on the performance of IOSCs with a structure of ITO/ZnONFs/P3HT:PCBM/MoO 3 /Ag. There is a 17.59% and 32.60% increase in the short circuit current and power conversion efficiency, respectively, after the treatment of the device for 20 seconds. Furthermore, the optimized device showed excellent stability under ambient conditions for more than four weeks without encapsulation. We conclude that the UV-ozone treatment oxidizes oxygen vacancy defects of ZnONFs, thereby decreasing the internal resistance and improving charge transfer at the ZnONFs/polymer interface. However, a longer treatment time will produce oxygen interstitial defects, which dramatically increases the work functions of ZnONFs and deteriorates the contact between ZnONFs and the active layer. As a result, the process of charge transfer will be blocked, resulting in a sharp drop in the performances of IOSCs.

Toward a Universally Compatible Non‐Fullerene Acceptor: Multi‐Gram Synthesis, Solvent Vapor Annealing Optimization, and BDT‐Based Polymer Screening

“…To improve the J SC and FF of our non‐fullerene acceptor, PDI‐DPP‐PDI to more closely match the performance of PC 60 BM controls we followed some recent literature methods to boost efficiencies through ZnO electron‐transport layer (ETL) modifications. In the method disclosed by Yin et al a brief post‐thermal annealing UV/ozone treatment of the ZnO layer was demonstrated to oxidize O 2 vacancy defects of ZnO and decrease the internal resistance to improve charge transfer at the interface with the active layer. Another ETL modification that has been widely adapted is the use of a polyethylenimine ethoxylated (PEIE) interfacial layer cast on top of the ZnO layer.…”

Energy level modulation of ITIC derivatives: Effects on the photodegradation of conventional and inverted organic solar cells

“…[16,19,[25][26][27] Little to no significant differences in J sc values for the three blend solar cells are observed, especially for the inverted devices (~14.5 mA.cm −2 ), which testifies to almost equal photon harvesting as shown in Figure s2c compared to the conventional devices may be due to the inherent structural defects in the ZnO layer. [28] Overall, the efficiencies are slightly lower than previously reported [16,[25][26][27] due to differences in device fabrication processes and conditions, however, the initial efficiencies do not much affect the general outcome of the study on device stability. All devices are processed under the same conditions unless mentioned otherwise.…”

Solution-Processed Organic and ZnO Field-Effect Transistors in Complementary Circuits

“…Naturally occurring oxygen vacancies in ZnO films may lead to trap sites that are detrimental to device performance. Several groups, including ours, have found that a UVozone treatment after film growth is an effective means of filling the vacancies [9][10][11]. This is seen to dramatically improve the performance of hybrid (with p-type organic semiconductors) photodiodes [12] and thin film transistors [13].…”

“…V O can result in charge-trapping mechanisms and thus degrade the performance of FETs. UV light soaking [9] and UV-ozone treatment [10][11][12] have been shown to reduce oxygen vacancies.…”