High Performance Photodetectors Based On The Perovskite/Organic-semiconductor Heterojunction

Photodetectors with high responsivity and detectivity,fast response speed and broadband responsivity have always been pursued by researchers.Perovskite-based photodetectors usually have large hysteresis phenomena.In order to obtain high performance photodetectors,the structure of the devices needs to be further optimized.The heterojunction between perovskite and other semiconductor materials can inhibit the recombination rate of photogenerated carriers,prolong the carrier lifetime,and improve the carrier responsivity and EQE(or gain).In this paper,photodetectors based on perovskite/organic semiconductors heterojunction have been studied.The results are as follows:1)The Cs-doped FAPbI₃ layer was prepared by using solution-based spin-coating approach,and the dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene(DNTT)film was deposited atop the perovskite layer through thermal evaporation to form a stacked heterojunction.By comparing the morphology of the film and the performance of the photodetectors,it is found that the photodetector based on FA_0.85Cs_0.15PbI₃ perovskite and90 nm DNTT layer has the best performance.The photodetector displayed broadband responsivity to illumination ranging from deep ultraviolet(DUV)to near infrared(NIR)light.Because of the gain,this device displays high on/off ratio,responsivity and detectivity values of 4.9×10⁴,778 AW^-1 and 1.04×10¹³ Jones under 450 nm at 3 V,respectively,which demonstrates that it has good detective ability for weak light.The response speed of the device(t_r/t_f=1.1 ms/2 ms)is very fast,and it has good repeatability and stability.2)A photodetector based on FA_0.85Cs_0.15PbI₃perovskite-[6,6]-phenyl-C₆₁-butyric acid methyl ester(PCBM)bulk heterojunction/DNTT hybrid heterostructure was fabricated by introducing PCBM into the FA_0.85Cs_0.15PbI₃ perovskite/DNTT heterojunction as the electron acceptor site.The PCBM selectively captures photogenerated electrons,which promotes the separation of electrons and holes and reduces the recombination between them.When the doping concentration of PCBM is1%,the photodetector has the best performance.Under 450 nm,the responsivity and detectivity can be enhanced to as high as 5.96×10³ AW^-1 and 7.96×10¹³ Jones,respectively.The t_r/t_f of the device increase with the increase of the amount of PCBM added.