Polyoxometalates Enhance The Photoelectric Properties Of Inorganic-Organic Hybrid Perovskite Materials And Photovoltaic Devices

Recently,the next generation of photoconductive materials,organic-inorganic hybrid perovskites have captured the attention of scientists and researchers in the field of energy conversion.The most important research topic is to improve light-to-electricity conversion property of the perovskite materials as well as enhance the perovskite-based photoelectric devices.Polyoxometalates（POMs）,a class of molecular metal-oxo cluster compounds have many superior physicochemical properties.The most intriguing property of POMs is that of acting as an electron acceptor that is able to separate the photogenerated excitons effectively,enhancing the photovoltage performance.In this paper,we introduced POMs into the perovskite material with the aim to enhance light-to-electricity conversion property of the perovskite materials and the photovoltaic performance of perovskite optoelectric devices.1.we prepared a perovskite–polyoxometalate composite by using a low-temperature and solution-processedmethod.The photoconductivity measurements manifested that the enhanced photocurrent of the CH3NH3PbI3/PW12 composite was ca.3-folds higher than that of the pristine CH3NH3PbI3.In addition,the enhanced photodetection performance of the composite was also revealed to be 82%（365 nm）and 177%（420 nm）higher than that of the pure perovskite device,respectively.Such enhancements in photoconductivity and photodetection performance should be attributed to the incorporation of POM,which provides a highly effective electron transfer pathway to separate the photogenerated excitons and reduce the electron–hole recombination.2.Based on the hole-conductor-free and fully printable PSC device,we introduced a POM（PW12）into the hybrid perovskite（5-AVA）x（MA）1-xPbI3 for enhancing the performance of PSCs.As a result,the device which containing PW12 exhibited an average PCE of 11.35%,which was a 24% increase with respect to the average PCE of the control device（9.17%）.We found that the addition of PW12 to perovskite could induce the growth of larger grains at the expense of small grains,a typical Ostwald ripening process,yielding larger grains with an average size of 30 mm.The large-grained perovskite film with higher crystallinity has certainly less crystal grain defects and facilitates charge transport.Therefore,the large-grained perovskite film growth induced by POM should be mainly responsible for the enhanced performance.3.We fabricate the fully printable perovskite solar cells in which the PW12/Ti O₂ acts as dense layer.The presence of POM provides a highly effective electron transfer pathway to separate the photogenerated excitons as well as to reduce the electron–hole recombination rates,and finally leading to an enhanced PCE from 9.42% to 10.65,which was a 13% increase with respect to the PCE of the control device.In addition,by electrochemical impedance spectra,we believe that the proper incorporation of POM can promote the electron transfer effectively,thus formation of electronic shallow trap.However,the excess POM will promote the electron-hole recombination,thus formation of electronic deep trap.4.We develope a unique means of making POM/Cu2 O composites by electrostatic attractive interaction in which [PW10Mo2O40]5-anions were adsorbed on Cu2 O crystal faces of positive charge.The introduction of POM could effectively improve the photovoltaic performance of Cu2 O electrode,because POM could act as an electron transfer mediator to retard the electron–hole recombination and facilitate the photoexcited electron transfer.