The Electrode Interface Modification Of Inverted Organic Photovoltaic Cells

Inverted polymer solar cells with higher stability, low fabrication cost show betterpreparation advantage compared with the normal device. How to obtain high powerconversion efficiency is the research hotspot in recent years. The interfaces and the energymatching between the active layer and the cathode or anode electrodes are crucial foreffectively collecting the charges. The work of this paper aimed at the above problems. Detailwork is summarized as follows:First, inverted polymer solar cells with the structure of ITO/CH3COOCs/P3HT: PCBM/MoO3/Ag were fabricated by thermal evaporation. Results show that device performanceparameters are improved with introduction of CH3COOCs. The optimal thickness of theCH3COOCs interlayer is1nm. Compared with the control device, the power conversionefficiency (PCE) enhancement of160%is obtained. The thickness of the anode MoO3modification layer is also optimized, the optimal thickness is1.5nm.Second, a solution-processed, work-function tunable, and low-temperature processedhybrid electron-collecting layer comprising a PEO and CH3COOCs is introduced for invertedpolymer solar cells. The ratio of the PEO to CH3COOCs is optimized in terms of themeasurements of work function and current-voltage characteristics. The hybrid interlayerlowers the work function of ITO from4.82eV to4.21eV measured by the Kelvin probe.Inverted polymer solar cell based on blends of poly(3-hexylthiophene)(P3HT) and[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) with PEO0.8:CH3COOCs interlayerexhibits enhanced PCE of2.82%under100mW/cm2AM1.5illuminations. The improvementwas ascribed to interfacial tuning of the ITO electrode. Besides, PEO: CH3COOCs canmodify the interfaces of ITO and the active layer to improve adhesion, compatibility,wettability for the hydrophobic organic active layer surface, resulting in better interfacialcontact and reduced contact resistance. This method of utilizing of solution-processed PEO:CH3COOCs interlayer is very attractive to the fabrication of cost-effective and roll-to-rollprintable flexible inverted PSCs due to its simplicity and is well suitable for large scaleproduction.Third, perovskite CH3NH3PbI3is introduced as additive in the P3HT: PCBM active layer.Normal and inverted device based on PEO: CH3COOCs are fabricated. The influence of thedifferent content of additives in the performance is investigated. The best efficiency isobtained when the additive content is0.5%.