Efficient And Stable Solar Cells Based On Organic-Inorganic Hybrid Perovskite Materials

Organic-inorganic hybrid perovskite has emerged as one of the most promising materials for photovoltaic applications due to its remarkable optoelectronic properties,such as large optical absorption coefficient,long carrier lifetime(~1 ?s)and high carrier mobility(~10 cm2 V-1 s-1).With these intriguing properties,the theoretical limited efficiency of perovskite solar cells(PSCs)is predicted to be 31% and the highest certified PCE of 22.1% has been recently achieved,indicating the great potential of PSC device in future photovoltaic industry.However,most of the fabrication processes of PSCs are strictly controlled in a dry or inner condition due to the air ambient stability of perovskite films and their devices.More seriously,several researches have demonstrated that the PSCs are instable under the light soaking condition due to the defects at interface between electron/hole transport and perovskite films.These questions haven't been well solved.In this article,we focus on the above issues of perovskite solar cells,introducing one-step solution process with excess methylammonium iodide(CH3NH3I,MAI)molar proportion(5%)to fabricate perovskite films in normal atmosphere,using a fullerene derivate of PCBDAN to modify TiO2 electron transport layer,and fabricating the inverted perovskite solar cells based on NiO hole transport layer.Those works have been carried out with detailed characterizations and in-depth discussions,the results obtained are as follows:(1)We introduce a simple strategy through a small increase in methylammonium iodide(CH3NH3I,MAI)molar proportion(5%)for perovskite fabrication in ambient air with a ~50% relative humidity.The analysis of morphology and crystallography demonstrates that excess MAI profits significantly the grain growth without decomposition.X-ray photoemission spectroscopy(XPS)demonstrates that no metallic Pb0 exists in the perovskite film and the I/Pb ratio is improved.The time-resolved photoluminescence(TRPL)measurement shows an efficient suppression of non-radiative recombination in perovskite layer.As a result,the device yields improved power conversion efficiency(PCE)from 14.06% to 18.26% with reduced hysteresis under AM1.5G illumination(100 mW/cm2).This work provides a feasible and low-cost way for the development of high-efficient PSCs in ambient air.(2)We have successfully introduced fullerene [6,6]-phenyl-C61-butyric acid 2-((2-(dimethylamino)ethyl)(methyl)-amino)-ethyl ester(PCBDAN)as an interfacial modifier for the TiO2 electron transport layer(ETL)in planar PSCs,which can significantly improve the photovoltaic conversion efficiency and light soaking stability of the devices.The quality of the perovskite film and electron extraction efficiency between the perovskite and ETL are both improved by introducing the PCBDAN interfacial layer.An improved power conversion efficiency(PCE)of 16.78% can be obtained for the device with PCBDAN under AM 1.5G illumination(100 mW cm2).And the light soaking stability of the planar device is greatly improved after modification.This work provides a feasible way by interfacial modification for the realization of highly efficient devices without light-soaking degradation.(3)We fabricate the inverted planar perovskite solar cells with NiO thin film deposited by spray pyrolysis to investigate the device stability in the ambient air.Combined with the modified perovskite deposition method,the NiO-based inverted planar PSC shows a considerate power conversion efficiency of 16.34% and a high EQE beyond 80% between the region from 300 nm to 850 nm with high stability.And the device shows fast response to the AM1.5G illumination.